Treating non-naturally occurring subsurface soil contaminants with pneumatic injection of dry media

ABSTRACT

A method for pneumatically fracturing a soil formation, and thereafter utilizing or maintaining the fracture network thus formed by continuous injection of a gas stream into the fracture network, and introducing into that gas stream dry media which is entrained in the gas stream and thereby dispersed and distributed through the soil formation in substantially predictable or predetermined patterns, is described. The fracture network and/or the dry media contained therein create or enhance usefulness for a given purpose with respect to the soil formation. The method utilizes novel apparatus, especially high velocity nozzles which are substantially planar or directional and can be used in combination with the borehole casing to achieve a variety of fracturing and dry media injection effects.

REFERENCE TO COPENDING APPLICATIONS

Attention is directed to application Ser. No. 08/515,463, filed Aug. 15,1995, now U.S. Pat. No. 5,560,737, entitled "Pneumatic Fracturing andMulticomponent Injection Enhancement of in Situ Bioremediation".

FIELD OF THE INVENTION

The present invention is in the field of methods and apparatus fortreating soil contaminated with non-naturally occurring compositions,especially chlorinated organic compounds, but also including radioactivewaste materials, comprising treating the soil in situ without having toremove the soil from the site. The present invention relates to methodsand apparatus for in situ subsurface soil remediation of contaminantsfrom the soil by the use of a gas injected into the soil at a givenlocation. The gas injection creates an artificial fracture network inthe soil to a substantial radius; and gas injection at high flow ratesand velocity is thereafter continued in order to maintain the fracturenetwork in a dilated state. A variety of dry, granular media can beinjected into this gas stream, where it becomes suspended and finallydeposited throughout the soil formation. The dry, granular mediafacilitates the soil remediation in a number of novel ways, dependingupon its composition, and includes the use of electrically conductivecompositions which establish a starter path for in situ vitrification ofthe soil formation, leading to isolation of the contaminants.

BACKGROUND OF THE INVENTION

The magnitude of subsurface contamination in the United States today issuch that it poses a serious threat, both in terms of the health ofhumans and wildlife near it, and with regard to the environment as well.The state of the technology available to clean-up subsurfacecontamination sites has often lagged far behind environmentalregulations; and when such technology has proven effective, it has alsousually been too expensive to employ.

Subsurface contamination may occur in a variety of soil formations. Theexpression "soil formation" as used herein is intended to mean anygeologic formation comprising soil, weathered rock, or sound rock, orany combination of these. Soil comprises unconsolidated mineral grains,while sound rock, i.e., bedrock, comprises consolidated or lithifiedaggregations of mineral grains. Weathered rock is sound rock in theprocess of becoming soil through the eroding activity of the elementsupon it. The methods and apparatus of the present invention areapplicable to all such soil formations, including bedrock. Althoughbedrock may contain natural fractures and voids, the present inventioncan be used to significantly increase the number and extent of suchfractures and voids.

The subsurface soils comprising the contamination sites to be remediatedby present invention are generally divided into two major zones, (1) theunsaturated zone, also known as the "vadose zone" and (2) the saturatedzone. Perched water zones are also included. The present invention isfully applicable to, and operable in, both of these zones, and isespecially suitable for non-cohesive soils such as granular sands andgravels, which do not fracture, in the conventional meaning of the term.The vadose zone extends from the ground surface down to the ground watertable. The saturated zone begins at the ground water table and extendsto a further depth. The vadose zone may be further divided intoadditional subzones, but will be treated as a single zone in the presentdiscussion. Since the vadose zone is the uppermost layer of theterrestrial environment, it is more likely to contain pathways for toxicand hazardous chemicals to enter groundwater systems.

Studies have shown that it is less costly to remove volatile organiccompounds (VOCs) from the vadose zone than to pump and treatcontaminated ground water. That is the reason for the current focus ontechnology for the in situ removal of VOCs from the vadose zone. Suchtreatment technologies include vapor extraction, biodegradation, soilwashing and thermal treatment. Vapor extraction is a process for the insitu removal of VOCs by mechanically extracting soil gases from thevadose zone through one or more vertically oriented perforated ventwells installed in the contaminated zone. Air is forced to travelthrough the pore space in the soil, causing volatilization of the liquidand adsorbed volatile organic compounds. The extracted soil gases arethen either vented to the atmosphere or into an emission control system,depending on the concentration. The two major embodiments of such vaporextraction processes which have been demonstrated successfully in fielduse are in situ air stripping and vacuum extraction. In situ airstripping employs a series of interconnected air injector vents whichare supplied with forced air by an above ground blower and manifoldsystem that forces the air into the soil through the perforated ventwells. A separate blower or vacuum pump and manifold system is used toapply negative pressure to air extraction vents to withdraw the soilgases. The injection and extraction vents are located alternately withinthe array of vent wells on the site. This approach functions best withhighly permeable soils, e.g., loose, sandy soils and has proven to bemuch less effective in tightly packed soils and in soils with a highclay content.

Biodegradation is another process which has been used effectively in thetreatment of soils contaminated with organic compounds. Inbiodegradation, or bioremediation, the ecological conditions in the soilare altered to enhance microbial catabolism or to cometabolise theorganic contaminant, thus transforming it into a simpler, non-toxicproduct. Indigenous microorganisms are utilized most often, althoughseeding of the soil with exogenous microorganisms is also possible.Microorganisms are either aerobic, anaerobic, or facultative anaerobic,which can grow either in the absence or presence of oxygen. The mosteffective treatment has been the aerobic microbial process. With thisprocess, oxygen and often nutrients are injected or infiltrated into thesubsurface environment, using wells or a percolation process. The majorfactors which affect the rate of biodegradation in the vadose zoneinclude: pH, temperature, water content, carbon content, clay content,oxygen, nutrients, the nature of the microbial population, acclimationand concentration. However, unfavorable reaction kinetics, low substrateconcentration and slow degradability of certain compounds remainsignificant problems.

Another major limiting factor in bioremediation has been the lowpermeability of the fine-grained soil layers present at many sites. Onthe other hand, a site contaminated with methylene chloride, n-butylalcohol, acetone and dimethylaniline, after three years of in situaerobic biological treatment, has had its contaminant plume reduced by90%. Reclamation of an aquifer contaminated with benzene, toluene, andxylene using biodegradation has been achieved, with emphasis on theimportance of oxygenating the subsurface environment, and in particularobtaining superior rates of biodegradation using hydrogen peroxide as anoxygen donor, compared to using the traditional technique of airsparging.

A method and apparatus for establishing, maintaining and enhancingmicroorganisms utilized to remediate groundwater or soils contaminationthrough the injection of nutrients and gases, using a cylindrical headwith radial apertures and a pointed lower end adapted to penetrate thesoil, and through which a fluid can be delivered, is disclosed inAlbergo et al. U.S. Pat. No. 5,133,625. The fluid, which may be a viablemicroorganism culture containing nutrients, or may be a gas whichpermits or enhances the growth of ambient microorganisms, is introducedinto a subsurface location under pressure through the apertures in thecylindrical head. The pressure is provided by a pump or other means, andis adjustable. However, Albergo et al. does not suggest the use of drymedia in accordance with the particular dictates of the presentinvention. In Billings et al. U.S. Pat. No. 5,277,518 it is suggestedthat an oxygen-containing gas can be used to provide microorganisms andnutrients to the subsurface, and that injection wells can be connectedto an air compressor for this purpose. In Payne et al. U.S. Pat. No.4,945,988, a sparging process and apparatus is modified by placing anoxygen separator along conduit lines leading to an aquifer downstream ofan air pump, which permits the delivery of air which is substantiallyoxygen free to the aquifer, or is oxygen enriched to the vadose zone,thereby preventing growth of aerobic bacteria in the aquifer, whilestimulating such growth in the vadose zone. In neither of thesedisclosures, however, is there any suggestion of pneumatic injection ofdry media and the formation of discrete granular lenses in theformation, which are continuous between the injection point and adjacentvent wells in the formation, as is provided by the present invention.

Another approach taken in the art to remediating contaminated soilformations in certain situations, especially where radioactive wastecontamination is involved, is to isolate the contaminated waste site byplacing around it a vitrified underground structure. This isaccomplished by solidification of soil by in situ melting andvitrification using heat generated in the soil itself between spacedelectrodes. An improvement in this process is described in Murphy et al.U.S. Pat. No. 5,114,277, which places an initially electricallyconductive material at the desired location and depth to start upvitrification underground and cause the melt to have a substantiallyplanar shape. However, unlike the methods utilized in the presentinvention, the initially electrically conductive material is transportedas a slurry or in a solution through horizontal boreholes, or by meansof conventional hydraulic subsurface fracturing technology well known inthe drilling arts.

Paramount among the limitations of the existing and emerging treatmenttechnologies applicable to the vadose zone is the permeability of thesoil formation being treated. The efficiency of in situ treatmentprocesses all decrease as the soil permeability decreases. For soilswith low permeabilities the existing processes are largely ineffective.Low soil permeability may be caused by a number of factors, includinghigh clay content, high soil density and high fluid viscosity. Anadvance in this area was made by Schuring et al., U.S. Pat. No.5,032,042, with the discovery that pneumatically fracturing of thecontaminated soil formation leads to a significant improvement in theresults obtained with a variety of in situ decontamination methods.However, there is no suggestion by Schuring et al. of pneumaticinjection of dry media and of the techniques required for doing so, orof the manner in which a variety of such dry media may be used toenhance various remediation technologies.

The method described by Schuring et al. for eliminating subsurfacecontaminants from soil includes the steps of a) pneumatically fracturingthe soil, including the steps of i) inserting a tubular probe partiallyinto a well in the soil such that at least one orifice of a nozzlefluidly connected with the tubular probe is positioned at apredetermined height; ii) providing a sealed area in the well onopposite sides of the orifice; and iii) supplying a pressurized gas tothe tubular probe which travels through the orifice into the soil toproduce a fractured soil formation; and b) transforming the contaminantsinto a different state to decontaminate the soil, after creation of thefractured soil formation. There is also described therein in generalterms the use of such pneumatic fracturing to provide nutrient seeding,although this is not defined, and there is no disclosure of specificdevices and methods which might be used to accomplish this generalobjective.

For the present invention, on the other hand, there is provided hereinample description of such features as novel directional and plate-typenozzles which are able to focus high flow velocities into the soilformation, creating planar voids of substantially 360° circumference, orof sectional arcs thereof, by a rapid pneumatic intrusion and cuttingaction, whereafter dry media in a dry carrier gas are injected rapidlyto fill the formation, in accordance with the guidelines providedherein. The present invention can be used in a number of ways to obtainincreased rates of contaminant reduction, removal, or isolation whichare dramatic.

SUMMARY OF THE INVENTION

In its broadest scope, the present invention is contemplated to comprisea method for pneumatically fracturing a soil formation, and thereafterutilizing or maintaining the fracture network thus formed by continuousinjection of a gas stream thereinto, and introducing into that gasstream dry media which is entrained in the gas stream and therebydispersed and distributed through the soil formation in substantiallypredictable or predetermined patterns, whereby the fracture networkand/or the dry media contained therein create or enhance usefulness fora given purpose with respect to said soil formation. Although thepresent invention is primarily concerned with remediation ofcontaminated soil formations, the methods and apparatus of the presentinvention are applicable to a wide range of activities and can bringbeneficial solutions to a number of problems that arise in connectionwith soil formations.

For example, the methods and apparatus of the present invention can beused to inject chemical agents into soil formations for the purpose ofmanaging plant life rooted in those soil formations, especially largerplants such as trees, shrubs and other nursery stock with substantialroot systems that penetrate the soil formation to a significant depth.This plant life management can be either for the purpose of encouragingand sustaining the healthy growth of such plant life, or for the purposeof eradicating it. Thus the chemical agents which are injected into thesoil formation in accordance with the present invention comprisenutrients, e.g., fertilizers, trace minerals, plant growth regulantsincluding root stimulants, compounds that improve the uptake of suchnutrients, compositions which improve the texture, workability orfriability of the soil, e.g., humus, manure, and biodegradable materialssuch as saw dust, ground shells, shredded bark and the like, andbeneficial microorganisms such as nitrogen-fixing bacteria; protectiveagents, e.g., anti-viral, antifungal and anti-bacterial agents,insecticides, miticides, nematocides, acaricides and other pesticides,or any other compound which can treat or prevent a plant disease whentaken up through the root system of that plant; and herbicides which,when taken up through the root system of the plant, will lead toeradication of that plant. This wide range of activities and beneficialeffects make the methods and apparatus of the present inventionespecially useful in a number of commercial and industrial enterprises,from the care and management of farms, parks, forest tracts, nurseries,golf courses, large estates and resorts, to the concerns of theindividual homeowner.

As another example, the methods and apparatus of the present inventioncan be used to inject propping agents, e.g., sand, fine gravel, sawdust, and ground shells, into soil formations for the purpose ofmaintaining the fracture network created by the pneumatic fracturing inorder to create subsurface drainage galleries. This drainage network canserve a number of useful purposes, e.g., improving access to water bythe root system of affected plants, improving the drainage in poorlydrained soil formations in order to restore the usefulness of affectedsurface areas, and rehabilitating septic systems and affected drainagefields. The in situ vitrification method of the present invention can beused to create subsurface vitrified masses not only for the purpose ofisolating contaminants within a soil formation, but for other beneficialobjectives as well. These include use in construction, e.g., to createor reinforce building foundations and supports for other structures; usein preventing subterranean water movement in order to improve theviability of lakes, streams and ponds or reduce the incidence ofsinkholes and the flooding of mines; and use in the repair of, orprevention of damage to, or leaks from, underground electrical power,telephone, television and fiber-optics cables, pipelines for naturalgas, oil and other fluids, and water mains and lines and septic andstorm sewer drains.

Where the methods and apparatus of the present invention are used toremove or isolate subsurface contaminants, the soil formation willespecially be one which is contaminated with non-naturally occurringcompositions, especially chlorinated organic compounds, i.e.,hydrocarbons, and is therefore in need of remediation. The dry media maybe selected from a number of different classes of compounds comprising alarge number of species, and will usually be under pressure at the pointof entrainment. Depending upon the transport mechanism involved in themovement of the dry media into the pneumatically fractured soilformation, the continuous injection of the gas stream into the fracturedsoil formation may serve to maintain the formation in a dilated state.

The method of the present invention has a number of resultant utilities,depending on the composition of the dry media, the nature andcomposition of the fractured soil formation, and the identity andconcentration of whatever contaminating compounds may be present. Forexample, reducing or eliminating non-naturally occurring contaminantsmay be accomplished by establishing an in situ bioremediation cellwithin a soil formation to degrade the contaminants. This method employsas the dry media, nutrient material which will enhance the growth andactivity of microorganisms already present in, or added to thecontaminated soil formation, which are capable of eliminating orreducing the contaminants by degrading or transforming them. Thesenutrient materials may comprise inocula, agents to generate the desiredpH, buffers to maintain said pH, and nutritive substances, especiallythose with a time release coating which can often be fragile, especiallyunder harsh injection conditions. As another example, injection ofchemically reactive dry media, e.g., zero valence metals, into a soilformation containing non-naturally occurring contaminants would beuseful because of the ability of such media to react directly with saidcontaminants, leading to their reduction by chemical and/or biologicalprocesses. Such a method, in accordance with the present invention, canbe used to either replace or supplement the reactive trench systemswhich are currently being employed for that purpose. As another example,where the dry media comprises a mixture of graphite particles and glassfrit, it may be used to establish an electrical conductive resistancepathway through selected portions of the soil formation to whichelectrical energy is then applied, which results in resistance heatingand vitrification of the selected portions of the soil formation, whichin turn results in encapsulation or some other equivalent isolation ofwhatever contaminating compounds may be present in the soil formation.

Accordingly, the present invention provides a method for pneumaticallyinjecting substantially dry media into a soil formation, which includesthe steps of a) pneumatically fracturing the soil formation, includingthe steps of i) inserting a tubular probe partially into the soilformation such that at least one orifice of a nozzle fluidly connectedwith the tubular probe is positioned at a predetermined height; and ii)supplying a pressurized gas on a continuous basis into the tubular probesuch that the resulting pressurized gas stream travels through the atleast one orifice into the soil to produce a fracture network in saidsoil formation; b) preserving said fracture network in a dilated stateor otherwise thereafter utilizing said fracture network, by maintainingcontinuous injection of said gas; c) introducing substantially dry mediainto said gas stream from an optionally pressurized supply of said drymedia, while maintaining the gas to media ratio in the range of fromabout 100 to 1 to about 10,000 to 1 on a volume to volume basis in orderto assure adequate dispersion and distribution of the dry media throughthe soil formation in predetermined patterns; d) continuing injection ofsaid dry media into said fracture network until the desired amount andpredetermined distribution pattern for said dry media have beenachieved; and e) as desired or necessary, repeating steps a) through d)on a sequential basis in order to treat additional portions of said soilformation.

The present invention provides a method for pneumatically injectingsubstantially dry media into a soil formation as described above,wherein the pressurized gas is compressed air; wherein there is utilizedadditionally a nozzle fluidly connected with the tubular probe, saidnozzle being a high velocity directional nozzle capable of deliveringthe pressurized gas to all or any significant circular section, i.e.,arc of the surrounding soil formation, i.e., from about 15° tosubstantially 360°, the section being either defined and fixed, or elsebeing determinable and selectable by operation of the nozzle, includinga substantially planar nozzle whose injection aperture is a 360° openingof a predetermined height, and wherein the internal junction of thenozzle means with the tubular probe comprises a forcing cone having auniform parabolic or functionally similar slope to provide maximumacceleration to the gas stream and its entrained dry media immediatelybefore entry into the soil formation; and wherein said dry mediacomprises one or more members selected from the group consisting of 1)silica, including sand and glass frit; 2) carbon, including graphite andpowdered charcoal; 3) powdered metals including copper, nickel, tin,zinc, iron, magnesium, aluminum, phosphorus, chromium, cadmium,palladium, platinum, or alloys and salts thereof; 4) beads and particlesof synthetic resin, including polymers, copolymers and terpolymers,e.g., polyacrylates including those prepared from acrylic andmethacrylic acid; polyolefins including those made from ethylene,propylene, and butylene; polyvinyl chloride; polystyrenes; polyesters;polyimides; polyurethanes; polyamides; and polycarbonates; and mixturesof any of these; 5) organic compounds capable of remediating a soilformation contaminated with non-naturally occurring compositions,especially chlorinated organic compounds, i.e., hydrocarbons, byoxidizing, reducing, or neutralizing said non-naturally occurringcompositions, e.g., dechlorinating chlorinated hydrocarbons, by reactingwith said non-naturally occurring compositions to producenon-contaminating reaction products, and by catalyzing the chemicaltransformation of said non-naturally occurring compositions intonon-contaminating products, including catalysis by enzymatic action; and6) compositions which promote the growth and activity of microorganismsin the chosen soil formation, e.g., direct release or time releasenutrient pellets, buffers, oxygen sources and inocula in granular orparticulate form.

Where the dry media comprises sand or glass frit, for example, themethod of injecting dry media of the present invention may be used toremediate preselected soil formations, because the injected dry mediacompletely fills the pneumatically induced fracture network in thosesoil formations, forming a discrete granular lens. This granular lens isalso referred to herein as a media lens, since it is formed through theinstrumentality of the dry media. Such a granular or media lenscomprises a matrix within the soil formation consisting of voids andchannels, and the matrix has a double-convex or related type of shape.Typically, a media lens will extend in a planar manner, usually forseveral feet, into the soil formation. Together, the lenses thus formedcan be made continuous between the injection point of the dry media andadjacent extraction wells installed in the formation, through which thecontaminants, particularly volatile organic contaminants, can be removedin a typical vapor extraction or pump and treat system.

Accordingly, the present invention provides a method for reducing,eliminating or isolating non-naturally occurring, subsurface, liquid orsolid contaminants from one or more soil formations, which includes thesteps of a) pneumatically fracturing said soil formation(s), includingi) inserting a tubular probe partially into the soil formation such thata nozzle fluidly connected with the tubular probe is positioned at apredetermined height, wherein said nozzle is a high velocitysubstantially planar nozzle whose injection aperture is a 360° openingof a predetermined height, or is a directional nozzle comprising apreselected or determinable fraction of the 360° opening, and whoseinternal junction with said tubular probe comprises a forcing conehaving a uniform parabolic or functionally similar slope to providemaximum acceleration to said gas steam and dry media to be entrainedtherein immediately before entry into the soil formation; and ii)supplying a pressurized gas on a continuous basis into the tubular probesuch that the resulting pressurized gas stream travels through saidaperture of said nozzle into the soil to produce a fracture network insaid soil formation(s); b) preserving said fracture network in a dilatedstate or otherwise thereafter utilizing said fracture network, bymaintaining continuous injection of said gas; c) introducingsubstantially dry media into said gas stream from an optionallypressurized supply of said dry media, while maintaining the gas to mediaratio in the range of from about 100 to 1 to about 10,000 to 1 on avolume to volume basis, in order to assure adequate dispersion anddistribution of the dry media through the soil formation inpredetermined patterns; d) continuing injection of said dry media untilsuitable amounts and predetermined distribution pattern for said drymedia have been achieved; and e) as desired or necessary, repeatingsteps a) through d) on a sequential basis in order to treat additionalportions of said soil formation(s); and where said contaminants arebeing reduced or eliminated, f) maintaining a low volume flow of saidpressurized gas throughout said fracture network and adjacent portionsof said soil formation(s), optionally with the assistance of means forexerting reduced pressure thereon, for a time sufficient to oxidize,reduce, neutralize, transform by reaction or catalysis or otherwisedegrade and/or remove said contaminants from said soil formation(s); orwhere said contaminants are being isolated, using in situ vitrificationas the means for producing such isolation, comprising: g) using as thedry media one or more compositions which when dispersed and distributedin the soil formation in suitable amounts and predetermined patternscreate conductive resistance starter paths; and h) applying electricalcurrent to the conductive resistance starter paths using at least twoelectrodes suitably placed in the soil formation, in an amount and for atime sufficient to produce electrical resistance heating of the soilformation in a melt zone between the electrodes to a temperature abovethe melting point of all or a portion of the soil formation sufficientto produce a solid, vitrified, isolating mass. The gas stream which isused in the initial pneumatic fracturing and then in the continuous flowduring which the dry media is introduced, is preferably not oxidizing oroxygen containing, since oxygen will have a tendency to oxidize thematerials from which the conductive resistance starter path is madeunder the conditions of vitrification, thus creating an open circuit andpreventing further vitrification.

It should be pointed out the choice of the gas or mixture of gases whichcomprise the pressurized carrier gas stream for the dry media will belargely dependent upon the properties and purpose of the dry mediainvolved, as well as, to some extent, the type of soil formationinvolved. For example, it was just mentioned that oxygen would not beespecially suitable for use with the mixture of graphite and glass fritused for in situ vitrification. Where the dry media is reduced ironparticles, i.e., elemental Fe, for dechlorinating a soil formationcontaminated with, e.g., trichloroethylene (TCE), an oxidizingatmosphere should also be avoided to prevent any unwanted side reactionwith the iron particles. In this case, nitrogen, N₂, is a suitablechoice for the carrier gas. Another important factor to be considered isthe potential for any undesirable interaction between the gas carrierand the dry media entrained therein. The gas carrier should be inert, atleast with respect to its effect on the dry media composition. Economicswill also, of course, be of considerable significance in making thechoice of carrier gas.

The present invention provides a method for reducing, eliminating orisolating non-naturally occurring, subsurface, liquid or solidcontaminants from one or more soil formations having low initialpermeability as described above, wherein the pressurized gas iscompressed air; wherein the reduced pressure exerted on the fracturenetwork and adjacent portions of the soil formation(s) is created by oneor more extraction wells having vacuum pumps attached thereto; andwherein one or more vent wells are created to supply additional amountsof air to the soil formation(s).

There is further provided in accordance with the present invention amethod for reducing, eliminating or isolating contaminants in soilformations as described above, wherein the soil is a non-cohesive soil,e.g., granular sands and gravels which do not exhibit brittle behaviorand, consequently, usually fail to form a fracture network. This methodis facilitated by the high velocity substantially planar nozzle of thepresent invention, whose injection aperture is substantially a 360°opening of a predetermined height, and whose internal junction with saidtubular probe comprises a forcing cone having a uniform parabolic orfunctionally similar slope to provide maximum acceleration to said gassteam and dry media to be entrained therein immediately before enteringthe soil formation. This nozzle creates planar voids by an action whichmay be described as pneumatic intrusion, or pneumatic cutting, whereby afracture network is established and by means of which the dry media isinjected into, and the contaminants may be removed from, the soilformation. In another embodiment of this nozzle of the presentinvention, instead of being substantially planar, i.e., at about a 90°angle to the vertical tubular probe, the portion of the nozzle havingthe 360° aperture slopes upward and/or downward and thus has an angle ofless than and/or greater than 90° with respect to the vertical tubularprobe, from about 30° to about 80° and/or from about 100° to about 150°.

Another method within the scope of the present invention is one forreducing or eliminating non-naturally occurring, subsurface, liquid orsolid contaminants from one or more soil formations by establishing anin situ bioremediation cell therein to degrade said contaminants. Thismethod follows the general procedures described above for other methods,but employs as the dry media, nutrient material which will enhance thegrowth and activity of microorganisms present in the contaminated soilformation, which are capable of eliminating or reducing the contaminantsby degrading or transforming them. These nutrient materials may compriseinocula, agents to generate the desired pH, buffers to maintain said pH,and nutritive substances, especially those with a time release coatingwhich can often be fragile, especially under harsh injection conditions.It is also necessary that the gas which is injected continuously be onewhich is oxygen-containing, e.g., compressed air or oxygen, where themicroorganism whose growth and activity are being promoted is an aerobicmicroorganism. Where the microorganism is anaerobic, on the other hand,a non-oxygen containing gas, e.g., nitrogen, must be used.

Yet another method within the scope of the present invention is one forreducing or eliminating non-naturally occurring, subsurface, liquid orsolid contaminants from one or more soil formations by introducingtherein chemical agents which reduce, oxidize, neutralize, cleave,decompose, chelate, complex, catalytically transform, or otherwiseentering into chemical reactions with said contaminants whereby thequalities which make them undesirable contaminants are permanentlyaltered. This method follows the general procedures described above forother methods, but employs as the dry media, a reactive chemical agentof some type. The specific chemical agent selected will be determined toa large extent by the composition of the contaminant present in the soilformation.

Yet another method within the scope of the present invention is one forisolating non-naturally occurring, subsurface, liquid or solidcontaminant zones within one or more soil formations by creatingvitrified underground structures which produce such isolation, either byencasement or otherwise. This in situ vitrification is accomplished byusing as the dry media in the method of the present invention describedabove, one or more compositions which will produce the amount ofelectrical conductivity and electrical resistance necessary to result inthe creation of conductive resistance starter paths. The dry mediacompositions are applied in amounts and predetermined patterns, at anydepth, and at any location in the soil formation, which will produce thedesired isolation after vitrification takes place. Thereafter,electrical current is applied to the soil formation through theconductive resistance starter paths by the use of electrodes in aconventional manner. As mentioned previously, the gas stream which isused in the initial pneumatic fracturing and then in the continuous flowduring which the dry media is introduced, is preferably not oxidizing oroxygen containing, since oxygen will have a tendency to oxidize thematerials from which the conductive starter path is made under theconditions of vitrification, thus creating an open circuit andpreventing further vitrification.

Another method within the scope of the present invention is one forreducing or eliminating non-naturally occurring, subsurface, liquidcontaminants from one or more soil formations which do not exhibitself-propping behavior, e.g., softer, sensitive clays, wherein there isused as the dry media a granular propping agent, e.g., sand, finegravel, saw dust, and ground shells. The method creates and maintains acontinuous plane of fluid flow channels which establish connectivity inthe soil formation and thereby accelerate contaminant treatment byconventional techniques such as the pump and treat system, or othermethods of the present invention described herein.

There is further provided in accordance with the present invention anapparatus for pneumatically injecting substantially dry media into asoil formation, which includes 1) fracturing means for pneumaticallyfracturing the soil formation, the fracturing means including a) tubularprobe means for receiving i) a pressurized gas, the probe meansincluding ii) a soil penetrating portion adapted to be inserted in awell or casing in the soil formation, and iii) an above soil portion influid communication with the soil penetrating portion, the soilpenetrating portion including tube means for receiving the pressurizedgas; b) sealing means, especially first and second packer meansconnected with the tube means for pressing against walls of the well orcasing so as to provide a sealed area in the well or casing between thefirst and second packer means; c) nozzle means preferably positioned inthe sealed area in fluid communication With the tube means for supplyingthe pressurized gas to the soil formation, said nozzle means fluidlyconnecting the soil formation with the tubular probe means, and being ahigh velocity directional nozzle capable of delivering the pressurizedgas to all or any significant circular section, i.e., arc of thesurrounding soil formation, i.e., from about 15° to substantially 360°,the section being either defined and fixed, or else being determinableand selectable by operation of the nozzle, including a substantiallyplanar nozzle whose injection aperture is a 360° opening of apredetermined height, and wherein the internal junction of the nozzlemeans with the tubular probe comprises a forcing cone having a uniformparabolic or functionally similar slope to provide maximum accelerationto the gas stream and dry media entrained therein immediately beforeentering the soil formation; and d) pressurized gas supply means forsupplying the pressurized gas to the above soil portion of the tubularprobe means, wherein the pressurized gas travels through the nozzlemeans into the soil to produce a fracture network; and 2) means forintroducing one or more dry media compositions into a pressurized gasstream subsequently to creation of the fracture network, wherein thepressurized gas, in conjunction with the dry media, deposits the drymedia in the fracture network, and wherein the pressurized gas has asufficiently high gas to dry media ratio to maintain the soil formationin a state of dilation while the dry media is distributed throughout thefracture network, or otherwise to accommodate or promote the transportmechanism governing such distribution, or otherwise thereafter toutilize the fracture network by maintaining a continuous injection ofthe gas into it; including a) separate supply means for independentlysupplying the one or more dry media compositions, including valve meansassociated With each supply means which control the flow rate and amountof dry media composition from each supply means; b) pump means forintroducing the dry media compositions under pressure into the abovesoil portion of the tubular probe means, coincidently with passagetherethrough of the pressurized gas; and c) pressure regulating valvemeans between the pump means and the above soil portion of the tubularprobe means to regulate and provide a sufficiently high gas to dry mediaratio to maintain the soil formation in a state of dilation while thedry media is distributed throughout the fracture network, or otherwiseaccommodate or promote the transport mechanism governing suchdistribution.

The apparatus of the present invention further provides apparatuscomprising nozzle means fluidly connecting the soil formation with thetubular probe means, and being a high velocity directional nozzlecapable of delivering the pressurized gas to all or any significantcircular section, i.e., arc of the surrounding soil formation, i.e.,from about 15° to substantially 360°, the section being either definedand fixed, or else being determinable and selectable by operation of thenozzle, including a substantially planar nozzle whose injection apertureis a 360° opening of a predetermined height, and wherein the internaljunction of the nozzle means with the tubular probe comprises a forcingcone having a uniform parabolic or functionally similar slope to providemaximum acceleration to the gas stream and dry media entrained thereinimmediately before entering the soil formation. Where the section of thesoil formation to be injected with dry media is determinable andselectable by operation of the nozzle, there will be included with thenozzle as a part thereof, means for selecting the section to be injectedwith regard to its relative size. With regard to its direction relativeto the soil formation, this is determined and selected based on markingson the well casing and tubular probe at the surface which correspond tothe location of the section selector means on the directional nozzle.

Directional nozzle means may also be employed which are used inconjunction with the borehole casing itself. In this embodiment of thepresent invention the custom borehole casing includes injection portslocated at predetermined intervals of depth and circumference throughwhich the dry media can be injected by the tubular probe withdirectional nozzle means attached at the end thereof. The dry mediainjection port of the directional nozzle is brought into register withthe injection port of the borehole casing, allowing the pressurized gaswith entrained dry media to be injected directly into the soilformation. The injection ports in the borehole casing may be equippedwith temporary plugs or with the protective closure means for dry mediaports described in detail further below. These serve the function ofpreventing grit and other unwanted materials from the soil formationfrom entering the borehole. A substantially planar nozzle may be used inconjunction with the custom borehole casing as described herein, byreplacing the directional nozzle with the planar nozzle. However, thiswould require that the injection ports in the custom borehole casing bevirtually circumferential. Since this is virtually an impossibility,portions of the custom borehole casing sufficient to provide therequired structural integrity must be allowed to remain. Sealing meansmust also be provided between the borehole casing and the tubular probe,above and below the dry media injection ports, in order to focus theforce of the pressurized gas directly on the soil formation immediatelyin front of the ports.

Directional nozzle means may also be employed which are used incombination with a self-advancing borehole casing to form a single unit.Such nozzle means are equipped with jetting ports opening in a downwarddirection through which high velocity pressurized gas is ejected inorder to cut through the soil formation to produce the borehole, whichwill typically be one characterized by low stability geologicconditions. These nozzles must also have protective closure means forblocking the dry media injection port(s) while the tubular probe isbeing advanced by drilling in order to prevent the entry of unwantedgrit and other materials from the soil formation into the dry mediaports while the drilling operation is being carried out. Without suchmeans, these materials will block the dry media injection ports andseriously impair the functioning of the nozzle. This problem does notarise in the course of those drilling operations in which the boreholeis first produced in a conventional manner and the tubular probe withnozzle means attached is later introduced into the completed borehole.The protective closure means for the dry media ports may be 1) of thetrapdoor type which have a hinged or sliding movement which may beassisted by springloading, e.g., a retractable door means; 2) of themitral valve type which employ a circular or parallel lateralarrangement of members which readily permit the movement of thepressurized gas in one direction while preventing the movement of gritand other materials from the soil formation in the opposite direction;and 3) of the one-way valve type which utilize a buoyant sphere movablewithin a cylindrical tube by either the pressurized gas in one directionor by the grit and other materials from the soil formation in the otherdirection, and are so configured that the buoyant sphere engages andseals a circular opening in one end of the cylindrical tube when movedin one direction, but is prevented from blocking the correspondingcircular opening in the other end of the cylindrical tube and oppositedirection, by a spacer element that permits the pressurized gas to flowaround it. Whatever protective closure means and nozzle design areselected, they should be characterized by the smallest possible numberof moving parts and should rely on the forces produced by thepressurized gas stream and by the soil formation for their operation, inorder to provide a nozzle which is functional and reliable and notlikely to result in significant down time for repair or replacement.

With regard to the substantially planar nozzle whose injection apertureis substantially a 360° opening, instead of being planar, i.e., at a 90°angle to the vertical tubular probe, the portion of the nozzle havingthe 360° aperture may slope upward and/or downward and thus have anangle of less than and/or greater than 90° with respect to the verticaltubular probe, from about 30° to about 80° and/or from about 100° toabout 150°. Optionally, a sealing means above the aperture of thenozzle, and preferably below as well, is included to ensure that theinjected gas stream is focused on a small area of the soil formation;the pressurized gas supply means includes compressor means for producingthe pressurized gas; one or more holding tank means for holding a supplyof the pressurized gas is provided; and valve means are used forconnecting the holding means with the tubular supply means in order toprovide a rush of the pressurized gas to the tubular probe means; meansare utilized for exerting reduced pressure on the fracture network andadjacent soil formation in order to maintain a low volume flow of apressurized gas through the fracture network; means for supplying thepressurized gas at a low volume flow are also provided, as well asoptionally means for passively supplying air to the soil formation.

The apparatus of the present invention further provides the meansdescribed above wherein the tubular probe comprises two or more,especially four, pipes inserted into the ground as a single unit, andwherein any one of the nozzle means described herein is positioned inthe sealed area in fluid communication with the tube means and the soilformation. This nozzle may be, e.g., a high velocity substantiallyplanar nozzle whose injection aperture is a 360° opening of apredetermined height, and whose internal junction with the two or morepipes comprises a forcing cone having a uniform parabolic orfunctionally similar slope to provide maximum acceleration to the gasstream and dry media to be entrained therein when injected into the soilformation from each of the two or more pipes. By selecting theparticular tube means into which the pressurized gas and/or entraineddry media is introduced, this embodiment permits the injection of two ormore dry media compositions into the soil formation, eithersimultaneously or serially. Where this embodiment is used, othermodifications of the apparatus of the present invention will berequired. For example, there will be a need for additional supply meansfor each of the dry media compositions, as well as additional pump meansand additional valve means.

In addition thereto, the apparatus of the present invention furtherprovides adjustment means for permitting relative movement between thefirst and second packer means in response to soil movement during a soilformation fracturing operation; including means for slidably connectingthe first and second packer means; and including wherein the means forslidably connecting includes a different diameter tube on which thesecond packer means is mounted, the different diameter tube beingslidable with respect to the tube means, sealing means for sealing thetube means with the different diameter tube, a rod connected to the tubemeans and extending through the tube means and out of the differentdiameter tube, and spring means engaged between the rod and thedifferent diameter tube for biasing the second packer means toward thefirst packer means while permitting relative movement therebetween.

The means for exerting reduced pressure on the fracture network is inparticular a vacuum pump connected to one or more extraction wells. Theoptional means for supplying air comprise outlying wells which arevented to the atmosphere in order to provide passive air inlets to thefracture network and adjacent soil formation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the apparatus used to carry outthe first step of pneumatic fracturing of the soil formation, into whichone or more dry media compositions are later to be injected.

FIG. 2 is a schematic cross-sectional representation of a portion of thebelow ground apparatus of the present invention for pneumatic fracturingof a soil formation and pneumatic injection of dry media therein,including a high velocity nozzle of the present invention, and a sealingmeans above the aperture of the nozzle to ensure that the injected gasstream is focused on a small area of the soil formation.

FIG. 3 is a schematic cross-sectional representation of the nozzle ofFIG. 2 showing additional detail such as the internal forcing cone withits uniform parabolic sloping sides, the bolts which anchor the bottomplate, and permit adjustment of the height of the 360° aperture, and thefillet weld by means of which the nozzle is attached to the tubularprobe.

FIG. 4 is a schematic cross-sectional representation of a tubular probecomprising four pipes inserted into the ground as a single unit, towhich a selective manifold is fluidly connected above ground, and towhich a directional plate nozzle is attached below ground, with itsinternal forcing cone positioned with its peak directly below the centerjunction of the four pipes.

FIG. 5 is a schematic cross-sectional side view representation of atubular probe comprising four pipes inserted into the ground as a singleunit, to which a directional plate nozzle is attached below ground, withthe internal forcing cone comprising four quadrant ramps, one for eachpipe.

FIG. 6 is a schematic cross-sectional top view representation of atubular probe comprising four square pipes inserted into the ground as asingle unit, to which a directional plate nozzle is attached, only thebottom plate of which is shown, and including directional baffles forfocusing the gas injection stream from each pipe in a specificdirection.

FIG. 7 is a schematic cross-sectional side view representation of atypical injection well where the tubular probe has first and secondpacker means connected thereto for pressing against the walls of thecasing so as to provide a sealed area in the casing between the firstand second packer means for the purpose of focusing the pneumaticinjection stream against several succeeding specific portions of thesoil formation.

FIG. 8 is a schematic cross-sectional side view representation of aborehole custom casing having dry media injection ports at predetermineddepth intervals, with which a substantially planar 360° dry mediainjection nozzle of the present invention is aligned.

FIG. 9 is a schematic cross-sectional side view representation of aborehole custom casing having a dry media injection ports at apredetermined interval both by depth and by circumference, with which adirectional nozzle of the present invention is aligned. A temporary plugfor another, unused dry media injection port in the borehole casing isalso illustrated.

FIG. 10 is a front view of a borehole custom casing showing the drymedia injection ports at predetermined intervals by depth andcircumference, as well as portions of the concealed tubular probetherein.

FIG. 11 is a cross-sectional view of a self-advancing directional nozzleof the present invention illustrating the jetting ports and dry mediainjection ports therein, as well as a protective closure means thereforcomprising a retractable shutter in the retracted or open position.

FIG. 12 is a front view of a self-advancing directional nozzle of thepresent invention illustrating the jetting ports and dry media injectionports therein, as well as portions of the concealed tubular probetherein.

FIG. 13 is a cross-sectional top view of the self-advancing directionalnozzle of FIG. 11 illustrating the annulus for the jetting ports, thejetting ports and dry media injection ports therein, as well as theprotective closure means therefor comprising a retractable shutter.

FIG. 14 is a cross-sectional top view of the self-advancing directionalnozzle of FIG. 12 illustrating the jetting ports and dry media injectionport, as well as the protective closure means therefor comprising aretractable shutter in the retracted position.

FIG. 15 is a schematic representation of the above-ground portion of afull-scale in situ vitrification system of the present invention whichemploys a graphite feed of the sand blast type.

FIG. 16 is a schematic representation of the above-ground portion of afull-scale apparatus of the present invention for pneumatic fracturingand dry media injection, including two dry media holding tank togetherwith the piping and valve means necessary for their operation.

FIG. 17 is a schematic cross-sectional view of a nozzle embodiment ofthe present invention which has substantially a 360° aperture, and inwhich flow of the pressurized gas stream is directed downward.

FIG. 18 is a schematic cross-sectional view of a nozzle embodiment ofthe present invention which has a 360° aperture, but in which the planeof the aperture is inclined from the perpendicular with respect to theaxis of the tubular probe.

FIGS. 19A, 19B, 19C are schematic representations of transportmechanisms for the dry media comprising interstitial transport ingranular medium, discrete fluidization in granular medium, and discretefracture in cohesive medium, respectively.

FIG. 20 is a schematic representation of apparatus of the presentinvention for carrying out in situ vitrification of a contaminated site.

FIGS. 21A, 21B, 21C, 21D are schematic representations of the manner inwhich in situ vitrification may be carried out on four different typesof contaminated sites comprising downward progressive vitrification,landfill encapsulation, spot vitrification, and bottom-up vitrification,respectively.

DETAILED DESCRIPTION OF THE INVENTION

In its broadest scope, the present invention is contemplated to comprisea method and apparatus for pneumatically fracturing a soil formation,and thereafter utilizing or maintaining the fracture network thus formedby continuous injection of a gas stream thereinto, and introducing intothat gas stream dry media which is entrained in the gas stream andthereby dispersed and distributed through the soil formation inpredictable patterns. Accordingly, the first step of the method is thepneumatic fracturing during which a sudden gas surge, typically ofcompressed air, imparts energy to the soil.

The first step involves pneumatic fracturing of the soil formation to betreated, where an injector nozzle within a fracture well creates aseries of fractures in the formation by the use of, e.g., high pressureand high flow rate compressed air. The second step involvespneumatically injecting one or more dry media compositions one or moretimes, usually on a periodic basis, into the soil formation beingtreated. The third step depends on the identity of the dry mediacomposition which has been injected. For example, if it is a proppantsuch as sand, then the third step will involve conventional vaporextraction procedures and equipment, so that extraction wells withvacuum pumps, and venting well for supplying additional air, will berequired. If, on the other hand, the dry media composition comprisesnutritive ingredients for the operation of an in situ biodegradationcell, then the fracture well will be converted to a low flow extractionwell by means of a vacuum.

Pneumatic Fracturing

Pneumatic fracturing injects air and/or other gases into a soilformation at high pressures and high flow rates in order to createcracks or fractures in the soil formation. The air or other gas, whichas a practical matter must be used in compressed form, is injected intothe soil formation at a pressure that exceeds the in situ stresses thatare present in the soil formation. The burst of air or other gas cracksthe formation and creates horizontal fracture planes which extend outradially from the point of injection. For example, when compressed airis injected into an isolated section of a borehole in accordance withprocedures described hereafter, the geologic formation involved willbecome stressed and eventually will fail when the breakdown pressure isreached. Upon failure, fractures will propagate perpendicular to theleast principal stress in the formation, i.e., the air will take thepath of least resistance. Low permeability soils tend to beover-consolidated, with the result that the least principal stress is inthe vertical direction. Consequently, fractures will tend to extendhorizontally from the injection point. Frequently, however, as theartisan is well aware, subsurface geological formations are not parallelto the earth's surface, but are at an angle thereto do to the action ofplate tectonics, which have caused uplifting and tilting of suchformations, with reference to the normal plane of the earth's surface.The pneumatic fracturing process greatly increases both the permeabilityand the exposed surface area of the soil formation, thus allowinggreater access to the areas of contamination.

High initiation pressures are not required to initiate shallowfractures, since fracture initiation pressures at depths of less than 20feet are less than 200 psi for rock formations, and 100 psi for soilformations. A more important factor than the injection pressure is theinjection flow rate. The greater the volume of air or other gas per unitof time injected into the soil formation, the further the resultingfracture will propagate, since the fracture initiation pressure ismaintained over a greater area of the soil. Accordingly, it is necessaryfor the pneumatic fracturing system to deliver the air or other gas notonly at high pressures, but also at high flow rates. Where thesecriteria are satisfied, it is possible to attain fracture radii inexcess of 25 feet. These pressure and flow rate requirements can usuallybe met most economically by the use of air compressors of the type whichare well known and readily available.

Since the present invention involves the pneumatic injection of drymedia compositions into a soil formation, as well as the pneumaticfracturing of that soil formation in preparation for such dry mediadelivery, an important criterion for successful application of themethod of the present invention is strict control of the pressures andflow rates of both the main, or fracturing and dilating, air or gasinjection system, as well as the auxiliary dry media injection system.An inverse relationship is maintained between the flow rates of thesetwo systems which together comprise the method of the present invention.As the injection of the dry media composition(s) is initiated, theamount of injected air is slowly decreased, thus maintainingapproximately the same original total air flow. Thus, an important, ifnot essential, feature of the auxiliary media injection system is itsability to efficiently disperse the dry media in the entraining gasstream. This is preferably done by direct pressure feed, which assuresthat the dry media composition(s) will fluidize prior to entering themain air or gas stream. The source of the pressure feed for the drymedia composition(s) is either an independent air or gas source, or aparallel by-pass tap of the main injection air flow.

Pneumatic Fracturing Apparatus

Typically, apparatus used to carry out the step of pneumatic fracturing,portions of which are depicted in FIG. I and the other figures of thedrawings, includes a tubular probe having a soil penetrating portion 1in fluid communication with an above soil portion 3. A double packerassembly 5 is connected to the lower end of the soil penetrating portionand includes an upper, elastic balloon-type packer 7 connected insurrounding relation to the soil penetrating portion, and a lower,elastic balloon-type packer 9 connected in surrounding relation to thesoil penetrating portion and in spaced relation to the upper packer.When the soil penetrating portion is placed within a larger diameterwell, and the packers are inflated, they tightly engage the walls of thewell so as to create a sealed area between the packers in the well. Anozzle portion 11 is formed as part of the soil penetrating portion,between the packers.

It has been found that the methods of the present invention can becarried out with a higher degree of proficiency and a greater degree ofsuccess by employing therein the novel high velocity directional orsubstantially planar nozzles of the present invention. These nozzles arecapable of delivering the pressurized gas to all or any significantcircular section, i.e., an injection arc of the surrounding soilformation, i.e., from about 15° to substantially 360°, the section beingeither defined and fixed, or else being determinable and selectable byoperation of the nozzle, including a substantially planar nozzle whoseinjection aperture is a 360° opening of a predetermined height. Whilethe directional nozzles are suitable for certain applications, and thesubstantially planar nozzles are suitable for other applications, asdescribed in more detail further below, overall, the directional nozzlesare the preferred embodiments of the present invention. The nozzles ofthe present invention are also characterized by the fact that theinternal junction of the nozzle means with the tubular probe meanscomprises a forcing cone having a uniform parabolic or functionallysimilar slope to provide maximum acceleration to the gas stream and itsentrained dry media immediately before entry into the soil formation.

Substantially Planar Nozzles

The substantially planar nozzle of the present invention is a plate-typenozzle which directs the injection stream horizontally into theformation in a very narrow plane, and then cuts or intrudes the geologicmedium of the soil formation instantaneously upon continuousintroduction of the pressurized gas stream. The nozzle also functions toaccelerate the gas to a higher velocity than it has in the tubularprobe, thus improving the ability of the gas stream to entrain, i.e.,transport and maintain in a suspended, i.e., dispersed condition, thedry media compositions which are introduced therein. As shown in FIG. 3,the nozzle 11 is attached by means of a sloping top portion 12 to thetubular probe 13 by the welding fillets 15, and additionally includesthe bottom plate 17 attached to the sloping top portion 12 by means ofthe bolts 19. The distance 20 between the sloping top portion 12 and thebottom plate 17 defines the aperture 21, and is maintained by thespacers 22, and is variable, depending on the height of the spacers. Theaperture 21 comprises a substantially 360° opening, i.e., it occupiesthe entire circumference of the nozzle 11, except for the bolts 19 andspacers 22, of which there are preferably only four, thus permittinginjection through the nozzle 11 into all four quadrants of the compass,i.e., the whole circumference of the surrounding soil formation in thewell. In the inside center of the nozzle 11 is the forcing cone 23,which has uniform parabolically sloping walls 25, and has its largerbase 27 connected in sealing relation to the bottom plate 17 by the bolt29. Thus positioned, the sloping walls of the nozzle cone direct thepressurized gas stream out through the aperture 21 and into thesurrounding soil formation. The substantially 360° aperture 21propagates fractures in all directions simultaneously, and has beenfound to be especially suitable for formations with low to moderatepermeability.

A variation of the substantially planar nozzle 11 described above, isshown in FIG. 5 and FIG. 6 for an embodiment of the present inventionwhich can be used for simultaneous or sequential pneumatic injection ofmore than one dry media composition. In the embodiment shown, thetubular probe comprises four square pipes are joined together, althoughonly two of these, 13 and 14, are shown in cross-section in FIG. 5. Thetop portion 12 is welded by fillets 15 to these pipes, while bottomplate 17 is welded to the junction of the four pipes 31, with thedistance 20 between the top portion 12 and the bottom plate 17 definingthe aperture 33, which is not, strictly speaking, a 360° aperture,because there is a corresponding aperture 35 slightly separated from itby the intervening pipe sections 37. In order to accomplish the sameacceleration of the gas stream that was achieved with nozzle 11 usingthe forcing cone 23, there is employed in this embodiment a forcing ramp39 in each pipe section. Some of the aspects of this embodiment appearmore clearly from the top cross-sectional view in FIG. 6, where pipes 13and 14 are shown atop bottom plate 17, with their cutaway portionsindicated at 41 and 43, respectively. The optional use of baffles isalso illustrated at 45.

Sealing Means During Fracturing

Returning to FIG. 1, the above soil portion 3 of tubular probe 2 isconnected through a quick release valve 4 to a holding or receiving tank6 having a pressure gauge 8 associated therewith in order to measure thepressure within the holding tank. The holding tank, which can be asingle tank, or a series of tanks 6 connected in series or parallel, inturn is connected to a compressor through a high pressure hose and airpurification unit (not shown).

In operation, after the drill rig drills a well, the soil penetratingportion with the double packer assembly is inserted down the well to afirst height. The air compressor then supplies pressurized air throughthe pressure hose and when the pressure within the holding tank(s)reaches a predetermined pressure, the quick release valve is opened toprovide a sudden rush of pressurized air down the soil penetratingportion of the tubular probe. The sudden rush of pressurized airproduces a first fractured soil formation. Thereafter, the double packerassembly and soil penetrating portion are inserted to a further depthand the operation is repeated to provide a second fractured soilformation, and so on. In many instances, after the soil formation hasbeen fractured, the soil will move. If the packers are fixed relative toeach other, undue stress on the packer assembly may result. Thus, in apreferred embodiment, a second packer is movable in the axial directionwith respect to a first packer. Specifically, the second packer ismounted to a smaller diameter tube, which is slidable within the nozzleportion. An O-ring seal or the like is provided therebetween to ensure asealed arrangement. An annular flange is provided in surroundingrelation to the smaller diameter tube near the upper end and normallyabuts against the lower end of the nozzle portion to provide anadditional seal prior to performing the fracturing operation. A rodextends through the smaller diameter tube, the nozzle portion and soilpenetrating portion, and is fixed within the soil penetrating portion bya spider assembly or the like. The opposite end of the rod extendingfrom the smaller diameter tube has a circular stop secured thereto, anda helical coil spring extends about the rod and is restrained betweenthe stop and the lower end of the smaller diameter tube, so as tonormally bias the smaller diameter tube, and thereby the second packer,toward the first packer. Upon fracturing of the soil by the sudden burstof air, the earth will separate, and accordingly, the second packer willmove with the earth apart from the first packer to maintain the sealedarrangement and to prevent damage to double packer assembly.

While the packer assembly described above is a preferred embodiment ofthe present invention, other embodiments have been found suitable andare still more preferred. For example, in FIG. 7 there is shown a doublepacker assembly 48 used within a well casing 47 to fracture a soilformation at more than one location. Since the assembly 48 is containedwithin a well casing 47, and the borehole 49 is grouted 51 to its fulldepth, the danger of damage to the packer assembly described above is nolonger present, and consequently, the features permitting the packers tobe slidably movable with respect to each other are no longer needed. Anadditional feature which may be employed with, or even instead of thepacker assembly in a well casing where the borehole is fully grouted, isshown in FIG. 2, where a "doughnut" seal 53, made from a suitablematerial, is placed above the top portion 12 of the nozzle 11. Thedoughnut seal prevents the borehole grouting 51 from coming in contactwith the top portion 12 of the nozzle 11, where it might otherwiseadhere to, or even block the aperture of, the nozzle 11. The doughnutseal also helps assure that the injected gas stream goes directly intothe surrounding soil formation, instead of being diverted up theborehole 49. Thus, the doughnut seal 53 duplicates to some extent thefunction of the packer assembly.

Dry Media Injection Apparatus

The various apparatus features described above may also be used in thecontext of the embodiments of the present invention which relate to theuse of a tubular probe for delivering more than one dry mediacomposition. The below ground portions of such a multi-pipe embodimentare schematically illustrated in FIG. 4, where four (4) nested riserpipes 55 are placed in a borehole 49 which has been filled with grout51. The riser pipes 55 terminate in the directional plate nozzle 11, towhich they are attached by weld fillets 15. The doughnut seal 53 ispositioned above the top plate 12 of nozzle 11, where it performs thesame function as with a single tubular probe. The bottom plate 17 ofnozzle 11 is attached to the top plate 12 by bolts 19, which havespacers 22 so that the opening of aperture 21 can be varied. In thisembodiment, nozzle 11 has a forcing cone 23 attached to bottom plate 17by bolt 29, instead of forcing ramps and optional baffles, as describedin another embodiment further above. Since this embodiment is intendedto deliver more than one dry media composition, there is also shown, forthe above ground portion associated with it, a selective manifold 57,which functions to selectively deliver, either simultaneously orsequentially, to any one or more of the riser pipes 55, a predeterminedamount of two or more, or any combination of several, dry mediacompositions. Further details concerning such a selective manifold areset out further below.

The nozzles used in the present invention are also important formaintaining the dry media in suspension, since it accelerates the air orgas stream to a higher velocity, which improves its ability to suspendor entrain the solid particles. The 360° nozzle propagates fractures inall directions simultaneously, and is suitable for formations with lowto moderate permeability. The nozzle having four quadrants, optionallywith forcing ramps, divides the total injection flow into one or more offour quadrants, thereby permitting the operator to focus the injectionenergy over a smaller arc radius of the surrounding soil formation. Thisembodiment of the nozzle is useful in very coarse grained formationswith a high permeability, since it focuses the injection energy in aspecific direction. It can be operated by successively injecting intoeach quadrant, resulting in four separate fracture lobes which merge toform a planar fracture or void. In other embodiments of this "quad"nozzle, two or three, or even five or more riser pipes are utilized, andthe corresponding 360° nozzle portion is divided into two, three, fiveand more sections, respectively. The injection nozzles are eithergrouted into the borehole if discrete levels are to be fractured, orthey may be mounted on a straddle packer assembly as described elsewhereherein. This "quad" nozzle could also be used if it were desirable tofracture the soil formation in a specific direction only, which wouldconvert this otherwise substantially planar nozzle into a directionalnozzle, i.e., one useful for focusing the pressurized gas stream and thedry media entrained therein onto an injection arc comprising somefraction of the 360° circle of surrounding soil formation. However,where it is desirable to use a directional nozzle, other more preferredembodiments of the present invention, described further below, would beused in preference to the "quad" nozzle.

Angular Nozzles

As has already been adverted to further above, subsurface geologicalformations are frequently not parallel to the earth's surface, but areat an angle thereto as a result of the action of plate tectonics, whichcause uplifting and tilting in such formations. Accordingly, where suchformations have been determined to exist, the efficiency of the nozzlesof the present invention can be improved by changing the angle of theplane of the aperture to the axis of the tubular probe. Thismodification allows the flow of the pressurized gas stream leaving theaperture of the nozzle to be directed in the same plane as the soilformation substratum. Where the plane of the soil formation substratumis parallel to the earth's surface, the substantially planar nozzledisposed at an angle of 90° to the tubular probe will be used.

Where the plane of the soil formation substratum is perpendicular ornearly perpendicular to the plane of the earth's surface, the nozzleshown in FIG. 17 may also be used, since the direction of the nozzle canbe easily modified. This nozzle can also be used as a replacement forthe substantially planar nozzle where the plane of the soil formation isparallel to the plane of the earth's surface, but where there is someconcern that using the substantially planar nozzle described above willcause too much disruption in the soil formation immediately adjacent thenozzle and thereby reduce its efficiency. The soil penetrating portion 1of tubular probe 13 has nozzle 11a attached thereto by means of filletwelds 15, with sloping top portion 12a, which together with bottom plate17a defines aperture 21, comprising a substantially 360° opening. Thebottom plate 17a is attached to sloping top plate 12a by bolts 19, whichhave spacers 22 so that the diameter of opening 20 of aperture 21 can bevaried. Within nozzle 11a is forcing cone 23a, which together withparabolically or functionally similar sloping walls 25a direct thepressurized gas stream out through aperture 21 and into the surroundingsoil formation at an angle calculated to be in approximately the sameplane as the plane of the soil formation substratum. This angle,indicated as 16, is the angle between the plane of nozzle 11a throughaperture 21, shown as 24 for a nozzle in a slightly different plane, anda plane 25 perpendicular to axis 26 of tubular probe. The parabolic orfunctionally similar slope of the nozzle walls serves to increase thespeed of the pressurized gas stream as it travels through nozzle 11a.This, together with angle 16 of a nozzle in a slightly different planefrom nozzle 11a, will maximize the effect of said gas stream and any drymedia entrained therein.

Where the plane of the soil formation substratum is neither parallel norperpendicular to the plane of the earth's surface, but is at some anglethereto, a nozzle such as the one shown in FIG. 18 may be used. Tubularprobe 13 has nozzle 11b attached thereto, with sloping top portion 12b,which together with corresponding bottom portion 17b defines aperture21, comprising a substantially 360° opening. Within nozzle 11b isforcing cone 23b, which together with parabolically or functionallysimilar sloping walls 25b direct the pressurized gas stream out throughaperture 21 and into the surrounding soil formation at an anglecalculated to be in approximately the same plane as the plane of thesoil formation substratum. This angle, indicated as 18, is the anglebetween the plane of nozzle 11b through aperture 21, shown as 24, andaxis 26 of tubular probe 13. The parabolic or functionally similar slopeof the nozzle walls serves to increase the speed of the pressurized gasstream as it travels through nozzle 11b. This, together with angle 18 ofnozzle 11b, will maximize the effect of said gas stream and any drymedia entrained therein. The presence of angle 18 in the design ofnozzle 11b may induce more of the gas stream to pass to one side thereofthan the other, due to gravitational effects. This tendency may becompensated for by the use of an adjustable baffle 10, which directs theflow of the pressurized gas stream.

The artisan will appreciate that angles 16 and 18, and especially 18,may be varied over a considerable range, depending upon andcorresponding to the angle between the plane of the soil formationsubstratum and the plane of the earth's surface. This may beaccomplished by the use of nozzles having fixed angles, such as thoseshown in FIGS. 17 and 18, or it may be accomplished by the use of anozzle having adjustable angles (not shown). The artisan will also beaware that it is not necessary to conform the angle of the nozzleexactly to the angle of the plane of the soil formation substratum,although the closer this angle is approximated, the more optimum will bethe results. The artisan will be still further aware that the dimensionsand other aspects of the nozzles of the present invention may be varieddepending upon such factors as the width of the bore hole and of tubularprobe 13. The width of aperture 21 may be varied depending upon thedesired volume and velocity of the pressurized gas stream passingtherethrough, and the character and amount of any dry media which may beentrained therein.

Nozzle and Borehole Casing Combined Use

Planar Nozzles

Substantially planar nozzles and directional nozzle means of the presentinvention may also be employed in conjunction with the borehole casingitself, as shown in FIGS. 8, 9, 10. In the embodiment of the presentinvention shown in FIG. 8, custom borehole casing 67 includes injectionports 69 located at predetermined intervals of depth and circumferencethrough which the dry media can be injected by tubular probe 70 withsubstantially planar nozzle means 72 attached at the end thereof. Drymedia injection ports 74 of substantially planar nozzle 72, havingaperture 21 with the indicated height, is brought into register withinjection port 69 of custom borehole casing 67, allowing the pressurizedgas with entrained dry media to be injected directly into the soilformation. Injection ports 69 in custom borehole casing 67 may beequipped with temporary plugs 76 or with the protective closure meansfor dry media ports described in detail further below. These serve thefunction of preventing grit and other unwanted materials from the soilformation from entering the borehole. Sealing means must also beprovided between custom borehole casing 67 and tubular probe 70, aboveand below dry media injection ports 74, such as balloon-type packers 7and 9, in order to focus the force of the pressurized gas directly onthe soil formation immediately in front of the ports.

Directional Nozzles

In the embodiment of the present invention shown in FIGS. 9 and 10,custom borehole casing 67a includes injection ports 69a located atpredetermined intervals of depth and circumference through which the drymedia can be injected by tubular probe 70a with directional nozzle means78 attached at the end thereof, which comprises dry media forcing ramp80. Dry media injection port 74a of directional nozzle 78, havingaperture 21 with the indicated height, is brought into register withinjection port 69a of custom borehole casing 67a, allowing thepressurized gas with entrained dry media to be injected directly intothe soil formation. Injection port 69a in custom borehole casing 67a maybe equipped with temporary plugs 76a or with the protective closuremeans for dry media ports described in detail further below. These servethe function of preventing grit and other unwanted materials from thesoil formation from entering the borehole. Sealing means must also beprovided between custom borehole casing 67a and tubular probe 70a, aboveand below dry media injection ports 74a, such as doughnut seals 53 and54, in order to focus the force of the pressurized gas directly on thesoil formation immediately in front of the ports.

Directional Nozzle and Self-Advancing Borehole Casing--Single Unit

Directional nozzle means may also be employed which are used incombination with a self-advancing borehole casing to form a single unit,such as those illustrated in FIGS. 11, 12, 13 and 14. The single unit 82comprises outer jetting pipe 84 defining jetting annulus 85, and innerdry media injection pipe 86, with directional nozzle means 88 at the endthereof, which comprises dry media forcing ramp 90, and which isequipped with jetting ports 92 opening in a downward direction throughwhich high velocity pressurized gas is ejected in order to cut throughthe soil formation to produce the borehole (not shown), which willtypically be one characterized by low stability geologic conditions. Drymedia injection port 94 of directional nozzle 88, having aperture 21with the indicated height, is constructed so as to be in register withinjection port 89 of outer jetting pipe 84. Directional nozzle 88 mustalso include protective closure means 96 for blocking dry mediainjection port while the tubular probe is being advanced by drilling inorder to prevent the entry of unwanted grit and other materials from thesoil formation into the dry media injection port 94 while the drillingoperation is being carried out. Without such means, these materials willblock dry media injection port 94 and seriously impair the functioningof directional nozzle 88. This problem does not arise in the course ofthose drilling operations in which the borehole is first produced in aconventional manner and the tubular probe with nozzle means attached islater introduced into the completed borehole. The protective closuremeans for the dry media ports may be 1) of the trapdoor type which havea hinged or sliding movement which may be assisted by springloading,e.g., a retractable door means such as that shown as 96; 2) of themitral valve type which employ a circular or parallel lateralarrangement of members which readily permit the movement of thepressurized gas in one direction while preventing the movement of gritand other materials from the soil formation in the opposite direction;and 3) of the one-way valve type which utilize a buoyant sphere movablewithin a cylindrical tube by either the pressurized gas in one directionor by the grit and other materials from the soil formation in the otherdirection, and are so configured that the buoyant sphere engages andseals a circular opening in one end of the cylindrical tube when movedin one direction, but is prevented from blocking the correspondingcircular opening in the other end of the cylindrical tube and oppositedirection, by a spacer element that permits the pressurized gas to flowaround it. Whatever protective closure means and nozzle design areselected, they should be characterized by the smallest possible numberof moving parts and should rely on the forces produced by thepressurized gas stream and by the soil formation for their operation, inorder to provide a nozzle which is functional and reliable and notlikely to result in significant down time for repair or replacement.

Preferred Embodiment Dry Media Injection System

A preferred embodiment for the dry media pneumatic injection method ofthe present invention, and apparatus means which may be used to carry itout, are shown schematically in FIG. 15. Supply means 59 comprises a drymedia feed system which is in fluid communication with a tube trailer61. The tube trailer 61 is the source of the gas stream, in this casecompressed air, which is used to carry out the pneumatic injection ofthe dry media, and is not only mobile, but is able to provide air flowat 2400 psi of sufficient duration, 45,000 SCF, to permit injection ofthe desired amount of dry media. For example, where the dry mediainjection system is used as a starter for in situ vitrification, the drymedia will comprise graphite, and the supply tank 59 will hold fromabout 50 to about 100 gal of graphite. A high-flow dome loaded regulator63 is used to control the flow rate and pressure of the injected air.The dry media injection system is operated in parallel to the mainpneumatic injection system, and preferably consists of one to severalcartridge-type reservoirs, such as that shown at 59. It is preferredthat all regulators and valves, such as those shown at 65, be remotelycontrolled electronically to protect the safety of operating personnel.

The ratio of pressurized gas to dry media should be within the broadrange of from about 100:1 to 10,000:1, on a volume to volume basis. Thetype of soil formation into which the dry media is being injected has asignificant impact on the ratio; and the fact that the ratio is based onvolume means that the heavier dry media compositions will also have animpact on the ratio. For example, where the dry media composition isgraphite, the preferred range will be from about 100:1 to about 1000:1,while a more preferred range will be from about 150:1 to about 600:1. Bycontrast, where the dry media composition is iron particles, the ratiowill be in the range of from about 500:1 to about 2000:1.

In another embodiment for supplying dry media in accordance with thepresent invention, the dry media supply tank may have its own compressedair supply in the form of a tube trailer, which supplies an air streamat the same pressure and for the same duration as its counterpart tubetrailer which supplies air directly to the tubular probe in the borehole. This is an alternate arrangement to that shown in FIG. 15, both ofwhich assure that the dry media is supplied to the injection gas streamunder pressure. It is necessary to exercise some caution with theembodiment involving two tube trailers, however, since there is somedanger of backflow at the junction of the conduit carrying the drymedia, and the main conduit for the gas stream.

The artisan will be aware of other means which are available fordispensing the dry media to the pressurized gas stream so that said drymedia will become efficiently dispersed and entrained therein. Suchother means which would be suitable include those known in thedispensing art, e.g., mechanical means such as auger driven feed devicesand those which utilize a fluidized bed of the dry media. Other suitabledevices may employ a Bernoulli valve that uses the movement of thepressurized gas stream to create a negative pressure which pulls the drymedia into the gas stream. However, despite the number of suitablemechanical dispensing devices which are available, it is still preferredto use a pressurized feed system for the dry media of the type describedabove, in carrying out the present invention.

It is often desirable in a process carried out in accordance with thepresent invention, to utilize two or more dry media compositions eithersimultaneously or sequentially. Such embodiments are accomplished by theuse of a multiple tank system or an array of cartridge-type feeders. Thecontents of each tank or cartridge can be metered by means of valveswhich regulate the flow of the gas stream into and out of each tank orcartridge. Any number of tanks or cartridges, as well as anycombinations thereof, may be employed. Thus, any combination or amountof dry media compositions can be used. After the dry media compositionsto be used are mixed together by being commonly entrained and agitatedin the gas stream, they then pass into the above-soil portion of thetubular probe, and are suspended in the high pressure, high flow ratestream of compressed air or other gas, passing through the tubular probeto the soil penetrating portion thereof, on its way to the injectionnozzle.

Preferred Apparatus

A preferred apparatus for carrying out the methods of the presentinvention is illustrated in FIG. 16, in which a compressed air source 97supplies pressurized gas for the entire system. The desired operatingpressure as well as the safety of the system are assured by pressurerelief valve 98 together with high-flow dome loaded regulator 100 whichis used to control the flow rate and pressure of the injected air. Theoperator of the system uses manual 11/2 inch ballvalves 104 to selectone of the following five (5) operating modes: 1) compressed air only tothe borehole for pneumatic fracturing; 2) compressed air through onlythe first, branch with a first dry media holding tank 106 then to theborehole for injection of the first dry media; 3) compressed air throughonly the second branch with second dry media holding tank 106 then tothe borehole for injection of the second dry media; 4) compressed airthrough both the first branch and the second branch with first andsecond dry media holding tanks 106 then to the borehole for injection ofthe first and second dry media mixed together; or 5) where the first andthe second dry media are the same, carrying out step 2) followed by step3) to the borehole for injection of the dry media for twice the amountand/or time otherwise possible. Dry media holding tanks 106 are"cartridge-type" reservoirs with a preselected capacity for dry media.Finer control of the flow path, flow rates and pressures of thecompressed air is controlled and determined by the 2 inch pneumaticballvalves 102 and the 1/2 inch pneumatic ballvalves 108, which allowthe operator to further control the compressed air flow to the borehole,and compressed air flow to dry media holding tanks 106. A line to eachholding tank 106 pressurizes the tanks and forces the dry mediacontained therein into the main compressed air stream. Sight glasses 110in the dry media holding tanks 106 permit the operator to observe themovement of dry media into the compressed air stream. The pneumaticballvalves 102 and 108 can be set within a wide range of variablepressures, which permits the operator to control the flow rate andpressure of the compressed air and the rate of entrainment of the drymedia in the compressed air stream. This multi-component injectionsystem improves both the control and reliability of the dry mediainjection process. All of the regulators and valves are pneumaticallyoperated but remotely controlled electronically in order to assure thesafety of operating personnel. Key process parameters, e.g., flow rate,pressure and ground surface heave, are monitored on a real-time basis topermit system control and adjustment during the dry media injectionprocess. These parameters may vary considerably, depending upon thenature of the dry media being injected and the application utilityinvolved, but the optimum parameter values are readily determined byroutine experimentation of the type described herein. For example, for apneumatic fracturing and in situ vitrification process, the system willbe typically be operated at from about 100 to about 600 psi, preferablyfrom about 200 to about 500 psi (3,450 kPa), delivering from about 500to about 2,500 scfm (118 m³ /s), preferably delivering volumes at thehigher end of the range, for a period of about 10 minutes. The deliveryrate of the graphite/glass frit media will usually be in the range offrom about 50 to about 100 lb/min (about 23 to about 45 kg/min).

Dry Media Compositions

The dry media which can be used in the practice of the present inventioncomprise a very large variety and number of different materials, theselection of all of which depends upon the particular applicationutility involved. Provided with the guidance afforded by the descriptionherein, however, the artisan of ordinary skill will be able to selectthe appropriate dry media for the specific application utility involved,and may even be able to suggest additional application utilities notspecifically recited here, and the dry media that would be suitable foruse in that utility. All such application utilities and the dry mediaused to accomplish and carry them out are contemplated to be a part ofthe present invention. In order to provide further guidance in thatregard, the groups and types of preferred dry media for use in thepresent invention comprise one or more members selected from the groupconsisting of 1) silica, including sand and glass frit; 2) carbon,including graphite and powdered charcoal; 3) powdered metals includingcopper, nickel, tin, zinc, iron, magnesium, aluminum, phosphorus,chromium, cadmium, palladium, platinum, or alloys and salts thereof; 4)beads and particles of synthetic resin, including polymers, copolymersand terpolymers, e.g., polyacrylates including those prepared fromacrylic and methacrylic acid; polyolefins including those made fromethylene, propylene, and butylene; polyvinyl chloride; polystyrenes;polyesters; polyimides; polyurethanes; polyamides; and polycarbonates;and mixtures of any of these; 5) organic compounds capable ofremediating a soil formation contaminated with non-naturally occurringcompositions, especially chlorinated organic compounds, i.e.,hydrocarbons, by oxidizing, reducing, or neutralizing said non-naturallyoccurring compositions, e.g., dechlorinating chlorinated hydrocarbons,by reacting with said non-naturally occurring compositions to producenon-contaminating reaction products, and by catalyzing the chemicaltransformation of said non-naturally occurring compositions intonon-contaminating products, including catalysis by enzymatic action; and6) compositions which promote the growth and activity of microorganismsin the chosen soil formation, e.g., direct release or time releasenutrient pellets, buffers, oxygen sources and inocula in granular orparticulate form.

Application Utilities for Dry Media

The methods and apparatus of the present invention find advantageousapplications in a number of in situ remediation technologies, wheretheir use can extend and improve the results obtained heretofore. Soilformations in need of such remediation contain volatile organiccompounds comprising hydrocarbons, especially petroleum hydrocarbons,including the products and byproducts of fuel production by crackingcrude oil; aromatic compounds, especially hydrocarbon aromaticsincluding benzene, toluene, xylene and similar organic contaminants;halogenated organic compounds, especially chlorinated hydrocarbons; andmore complex organic compounds, such as those which are the products orbyproducts of chemical manufacturing. Organic compound contaminantswhich are "volatile", as that term is used in the present invention, arethose which have a relatively high vapor pressure and can be found invapor form at relatively low temperatures. However, there is alsoincluded within the definition of "volatile organic compounds" (VOCs),as that term is used in the present invention, organic compounds whichare "volatilizable", i.e., capable of being made volatile.

The dry pneumatic injection of dry media compositions into soilformations achieved with the present invention, avoids all of the manydisadvantages which attend the use of liquid processes, e.g., hydraulicfracturing. These include dispersion of the contaminants in the soil,collapse of venting pathways, and viscous resistance. The dry mediainjection process of the present invention can be used to enhance suchremediation technologies as bioremediation, vitrification, vaporextraction, pump and treat methods, and chemical reduction. The drymedia injection process of the present invention also possesses a numberof advantages over existing technologies. For example, in geologicformations with low to moderate permeability, the inventionpneumatically creates artificial fractures which extend to substantialradii. Pneumatic injections are used initially to create an artificialfracture network in the soil formation. In the case of cohesive soilswith low to moderate permeability, this fracture network is formed as aresult of brittle failure of the formation and its propagates tosubstantial radii, usually from about 15 to 50 feet. The fracturepropagation also results in greatly enhanced air flow throughout theformation. It has been found that postfracture air flows of the mainfracture well are from about 13 to 178 times higher than prefracture airflows.

In non-cohesive soils, on the other hand, which have moderate to highpermeability, the invention pneumatically cuts the soil formation toestablish a planar void. Granular sands and gravels are examples of suchnon-cohesive soils, and they do not exhibit brittle behavior, and thusdo not fracture in the conventional sense. As described above, the novelplate-type nozzle of the present invention is unique in its ability toprepare such soils for the injection of dry media, as a result of itsability to create planar voids by means of a pneumatic intrusion orpneumatic cutting action. This mechanism of action was observed anddelineated by bench scale experiments using Plexiglass® brandpolyacrylate test tanks. Each planar void which was created wasmaintained in a dilated state for a period of a few minutes. Aperturesranged from 1 to 6 inches. The high velocity planar nozzle has beenspecifically designed to focus the air jet over a discrete area of thesoil formation, maximize the exit velocity of the air into theformation, minimize the pressure loss, and minimize the cloggingpotential of the dry media as it enters the formation.

An important aspect of the dry media pneumatic injection system of thepresent invention is the ability of the dry media to form a continuousplane which then establishes connectivity in the formation. This aspectof the present invention may be used in a number of valuableapplications, e.g., accelerating contaminant treatment in the soilformation. It has been found that the injected dry media completelyfills the fracture network created by the pneumatic fracturing andsubsequent gas flow, forming a discrete granular lens in the formation,which can be made continuous between the injection point for the drymedia and adjacent wells established in the formation, e.g., forextracting vapor. This connectivity feature can be used in a variety ofways, depending upon the remediation process involved. Vapor extractionor pump and treat remediation processes can be enhanced by establishinga sand lens which serves as a proppant, as well as a channel for fluidflow. In bioremediation systems, the media can consist of nutrients,buffers, oxygen sources and inoculum in a granular form, to enhancesubsurface microbial activity. For in situ vitrification processes,graphite can be injected to serve as an electrically conductive starterpath for melt initiation. Bench scale experiments have been conducted inwhich a mixture of graphite and glass frit was injected into a test soilin order to connect two carbon electrodes installed vertically in aPlexiglass® brand polyacrylate test tank. The continuity of the graphitelens was verified electrically by applying a variable voltage across theelectrode. The thickness of the graphite/glass frit layer ranged from0.5 to 2 inches. The improvement in electrical conductivity for theseexperiments ranged up to 833 times.

It is possible to vary the lens thickness of the injected media,depending upon the specific remediation application involved. A solidlens of dry media from one to several centimeters in thickness can beused where a continuous, porous lens is desired. Yet, in otherapplications, it is appropriate to inject only a limited amount of drymedia to act as a dispersed proppant. This technique has the advantageof allowing some open fracture flow to also occur in the soil formation,which is typically more efficient than solid porous media flow. Thisresults from the fact that flow in open fractures is governed by thecubic law, while flow in filled fractures is governed by Darcy's law.However, installation of a dispersed proppant requires carefulsequencing of the injection in order to avoid excess packing in thefracture.

Another advantageous feature of the present invention is the ability toinject fragile dry media without serious disruption of its physicalmakeup. An example of dry media which is susceptible to damage duringinjection is a material which has a time release coating on it to form apellet, so that the contents of the pellet are released into the soilformation over a period of time. Time release nutrient pellets toenhance the growth and activity of microorganisms in the soil formationare an example of such fragile dry media. It has been possible, inaccordance with the methods and apparatus of the present invention, toaccomplish pneumatic injection of such fragile dry media withoutsignificant damage to the media. This has been accomplished in oneembodiment by incorporating gradual flow transitions within the pipingnetwork in order to minimize turbulence and eddying of the carrier gas.Further, potential impact points on the internal surfaces of theinjection system have been coated with a resilient polymer which reducesthe potential for abrading and pulverizing of the fragile media. Inanother embodiment, powdered graphite which acts as a lubricant, hasbeen mixed together with, or dispensed along with, the dry fragile mediaduring pneumatic injection. These measures are critical especially inthe case of time release coatings, since damage to the time releasecoating essentially destroys the effectiveness of the media, and mayeven prove to be more harmful than if no media had been injected at all.

The methods and apparatus of the present invention for pneumaticinjection of dry media into soil formations has been found to beapplicable to a wide range of hydrogeologic conditions. The presentinvention can be applied to the vadose zone, the saturated zone, andperched water zones at contaminated sites. It is a significant advantageof the present invention that soil moisture does not interfere with thetransport of the dry media into the soil formation, as a result of theelevated air pressures which are used in the present method. There isadditional versatility in the methods and apparatus of the presentinvention with regard to the lithology and stratigraphy of a givencontamination site, since they can be used in rock as well as soilformations.

The pneumatic fracturing and dry media injection methods and apparatusof the present invention provide many advantages over such prior artprocesses as hydraulic fracturing, which, as the name implies, is afundamentally liquid system. It uses water, slurry, or other liquidagents to create the fractures and carry the granular media into thefracture network. Hydraulic fracturing uses large amounts of liquid tocreate the fractures, transport the media, and flush Out the polymercarriers. These liquids can remobilize the contaminants in the soilformation, however. Pneumatic fracturing not only avoids these problems,but offers such advantages as the promotion of microbial growth, thusenhancing bioremediation. Another significant advantage relates to theconsiderable difference between the flow viscosity of air or other gascompared to that of hydraulic injection fluids. Because the flowviscosity of air is much lower, the pneumatic injection and dry mediatransport aspects of the present invention can be carried out at muchhigher flow rates than are possible with hydraulic methods, thus greatlyincreasing the overall productivity and efficiency of the method of thepresent invention over such prior art methods. Yet another importantadvantage of the method of the present invention results from itsability to focus treatment on discrete zones within a much largergeologic formation. Thus, it is possible to treat a contaminated zonewith virtually surgical precision in directing dry media compositionsthereto which are to be used in its remediation. The methods of thepresent invention can also be applied to soil formations on whichbuildings have been erected or in which utility lines have been buried,with only the most minimal disruption of the sites involved.

For example, a method within the scope of the present invention is onefor reducing or eliminating non-naturally occurring, subsurface, liquidor solid contaminants from one or more soil formations by establishingan in situ bioremediation cell therein to degrade said contaminants.This method follows the general procedures described above for othermethods, but employs as the dry media, nutrient material which willenhance the growth and activity of microorganisms present in thecontaminated soil formation, which are capable of eliminating orreducing the contaminants by degrading or transforming them. Thesenutrient materials may comprise inocula, agents to generate the desiredpH, buffers to maintain said pH, and nutritive substances, especiallythose with a time release coating which can often be fragile, especiallyunder harsh injection conditions. It is also necessary that the gaswhich is injected continuously be one which is oxygen-containing, e.g.,compressed air or oxygen, where the microorganism whose growth andactivity are being promoted is an aerobic microorganism. Where themicroorganism is anaerobic, on the other hand, a non-oxygen containinggas, e.g., nitrogen, must be used.

Another application utility for the methods of the present invention isone for reducing or eliminating non-naturally occurring, subsurface,liquid or solid contaminants from one or more soil formations byintroducing therein chemical agents which reduce, oxidize, neutralize,cleave, decompose, chelate, complex, catalytically transform, orotherwise entering into chemical reactions with said contaminantswhereby the qualities which make them undesirable contaminants arepermanently altered. This method follows the general proceduresdescribed above for other methods, but employs as the dry media, areactive chemical agent of some type. The specific chemical agentselected will be determined to a large extent by the composition of thecontaminant present in the soil formation.

Another application utility is one for isolating non-naturallyoccurring, subsurface, liquid or solid contaminant zones within one ormore soil formations by creating vitrified underground structures whichproduce such isolation, either by encasement or otherwise. This in situvitrification is accomplished by using as the dry media in the method ofthe present invention described above, one or more compositions whichwill produce the amount of electrical conductivity and electricalresistance necessary to result in the creation of conductive resistancestarter paths. The dry media compositions are applied in amounts andpredetermined patterns, at any depth, and at any location in the soilformation, which will produce the desired isolation after vitrificationtakes place. Thereafter, electrical current is applied to the soilformation through the conductive resistance starter paths by the use ofelectrodes in a conventional manner. The gas stream which is used in theinitial pneumatic fracturing and then in the continuous flow duringwhich the dry media is introduced, is preferably not oxidizing or oxygencontaining, since oxygen will have a tendency to oxidize the materialsfrom which the conductive starter path is made, thus creating an opencircuit and preventing vitrification.

Another application utility within the scope of the present invention isone for reducing or eliminating non-naturally occurring, subsurface,liquid contaminants from one or more soil formations which do notexhibit self-propping behavior, e.g., softer, sensitive clays, whereinthere is used as the dry media a granular propping agent, e.g., sand.The method creates and maintains a continuous plane of fluid flowchannels which establish connectivity in the soil formation and therebyaccelerate contaminant treatment by conventional techniques such as thepump and treat system, or other methods of the present inventiondescribed herein.

Dry Media Transport Mechanisms

After a soil formation has been fractured and dilated, dry granularmedia compositions are pneumatically injected into the soil formation.In one embodiment of this process, while the soil formation is beingmaintained in a dilated state by the continuous injection of pressurizedair or other carrier gas therethrough, dry granular media is injectedinto the air or other carrier gas stream under pressure, whereupon itbecomes transported into all of the fractures and voids of the fracturenetwork which has been created in the soil formation. High air flow rateand velocity are maintained to keep the granular media suspended untilits deposition in the formation. The selection of the dry media dependson the specific application for which it is to be used, and customizedblends can be used in many instances. Bench scale experiments have shownthat when the discrete fractures or voids, which are created byfracturing and maintained in a dilated state by continuous air flow, arefilled by the injection of the dry media, that the thickness of themedia lenses ranges from 1 to 3 inches. The term "media lens" as usedherein refers to voids and channels which have a double-convex orrelated type of shape, which are created in the soil formation andextend in a planar manner therethrough and are subsequently filled byinjection of dry media. Typically, such a media lens has been found toextend in a planar manner, usually for several feet, into the soilformation. As a consequence of the formation of such media lensesthroughout the soil formation, considerable quantities of dry media mustbe delivered to the formation. The pneumatic injection system of thepresent invention is capable of producing mass flow rates in the rangeof 42 to 116 lbs. of dry media per minute, which is a rate of injectionsufficient to fill subsurface fractures in a matter of minutes.

In order to improve the efficiency of the dry media injection processesof the present invention, it was deemed important to obtain a betterunderstanding of the basic transport mechanisms by which the solidparticulate dry media were dispersed and distributed through varioussoil formations. In order to study these phenomena, mixtures of glassfrit and graphite were injected into soil formations as part of an insitu vitrification process. The starter path established by thesubsurface pneumatic injection process must have sufficient continuityand thickness to transfer the electrical power required to initiatevitrification. Once a melt is initiated, the resistance of the lens ofmolten soil will decrease making it electrically conductive. The heat isthen transferred to adjacent layers, thereby sustaining thevitrification process. Previous studies have shown that the electricalresistance of the starter path must be 50 ohms or less to initiate amelt. See Luey and Seiler, "Evaluation of New Starter Path Geometriesfor In Situ Vitrification", PNL-10122, Pacific Northwest Laboratory,Richmond, Wash. (1994). As a comparison, the resistivity of natural soiland rock formations is typically in the range of 1,000 to 100,000ohm-feet.

Although liquid-solid transport in geologic formations has receivedextensive study in the petroleum and water well industries with regardto enhancing hydraulic fracturing, the rheology and propagationvelocities of hydraulic fracture fluids are significantly different fromthose which characterize the pneumatic injection system of the presentinvention. Furthermore, studies on gas-solid transport in geologicformations have been very limited. See Gottschling et al., "Nitrogen Gasand Sand: A New Technique for Stimulation of Devonian Shale", Journal ofPetroleum Technology, May, 901-907 (1985). Accordingly, it has beenuseful to model solid particle transport in gaseous fluid streams withingeologic formations.

Interstitial Transport in Granular Medium

The three fundamental mechanisms of transport which are thought tocontrol the pneumatic injection processes of the present invention areillustrated in FIGS. 19A, 19B, 19C. The first transport mechanism,depicted in FIG. 19A, involves transport of the injected dry mediathrough the interstices of the geologic formation, i.e., soil formation.The necessary condition for interstitial transport occurs when the meandiameter of the injected particles is smaller than the effectivediameter pore spaces in the geologic formation. In commercial fieldapplications, this is not expected to be a primary transport mechanismas a result of the usual ratio of these diameters. This mechanism willconstitute an important secondary transport process, however, as theinjected dry media penetrates the surface boundaries of the injectedmedia lens. Under these conditions, it will have a significant effect ongas leakoff into the soil formation, and will, therefore, affect bothparticle transport and fracture propagation.

Three basic mechanisms have been identified which limit interstitialparticle migration through soil, as the result of studies of filterbehavior and filter criteria. See McDowell-Boyer and Sitar, "ParticleTransport Through Porous Media", Water Resources Research, 22(13),1901-1921 (1986). These mechanisms are surface caking, straining, andphysicochemical processes. For dry media pneumatic injection, it isexpected that either straining or caking will predominate, depending onthe ratio of mean dry media diameter, d_(m), to the mean soil particlediameter, d_(p). Penetration criteria can be developed by analyzing thestatistical particle distribution and shape of both the dry media andthe matrix, i.e., geologic formation. These criteria can be verifiedusing a horizontal infiltrometer operated under variable pressuregradients, so that the effect of each mechanism on formation leakoff canbe modeled and predicted. These criteria are expected to take thefollowing "form" ##EQU1##

where ψ, ξ, and δ are constants, established by analytical andexperimental methods.

The second transport mechanism is transport through a fluidizedaggregate lens, as illustrated in FIG. 19B. This mechanism occurs whenthe treated formation is cohesionless and the injected gas velocitiesare sufficient to keep the geologic particles in suspension. The porespace dilation and oscillatory particle motion allows passage of theinjected solid media through the fluidized geologic matrix. Theaggregate fluidization phenomenon has been studied in the chemicalengineering field of fluidized bed reactors. See Davidson and Harrison,Fluidization, Academic Press, New York, N.Y. (1971). Exploratoryexcavations of the dry media injected lenses of the present inventionhave suggested that this mechanism is the primary transport mechanismwhere the soil formation comprises coarse textured sands and gravels. Aprincipal concern with this transport mechanism is maintenance of adilute condition of the injected dry media with respect to the carriergas in order to prevent clogging, and to achieve maximum dry mediapenetration of the soil formation. Matrix segregation and mediadegradation during injection are also of concern. The minimumfluidization velocity is a function of soil porosity, shape and sizerange of the particles, and the viscosity of the injection fluid. Thepressure drop-velocity relationship in a fluidized bed is expressed bythe following equation at incipient fluidization Ergun, Chem. Eng.Progr., 48, 89 (1952)!: ##EQU2## ΔP_(B) pressure drop across fluidizedbed H_(mf) bed height at incipient fluidization point

U_(mf) minimum fluidizing velocity

μ viscosity of the fluid

ρ_(f) density of the fluid

ε_(mf) bed voidage at incipient fluidization point

However, fluid-particle interactions in a fluidized bed are differentfrom those occurring during fluidization in pneumatic injection of drymedia. The direction of the fluid flow for the former is in the sameplane as the gravitational forces, while it is perpendicular in thelatter. The fluid-particle interactions of gas jets in fluidized beds,discharging in the horizontal direction, provide a close parallel to thefluidized state which occurs during pneumatic injection of dry media.

The third transport mechanism is particulate movement through adiscrete, open fracture, as illustrated in FIG. 19C. This condition isencountered when the integrated dry media injection process is appliedto fine-textured cohesive formations such as clay and bedrock. Theseformations have a naturally low permeability and thus can sustain apressurized, discrete fracture. In this transport mechanism, theparticles remain suspended as long as the critical suspension velocityis maintained. As velocities attenuate radially away from the injectionpoint, particle transport changes to saltation and banking. The field ofsediment transport provides models for this transport mechanism. SeeBoggs, Principles of Sedimentology and Stratigraphy, Merrill PublishingCompany, Columbus, Ohio (1987). The change in concentration of particlesin the injection stream with increasing distance from the source, whicheffects the particle distribution within the fracture, can beapproximated by the equation which expresses two phase flow betweenhorizontal parallel plates with turbulent flow: ##EQU3## h distancebetween the parallel plates N_(p) airborne concentration of particles atthe source

N_(A) airborne concentration of particles at a distance from the source

u velocity of the fluid

v_(s) terminal settling velocity of the particles

l distance from the source

Studies of this transport mechanism include analysis of spatial andtemporal distribution of the injected media, graphite, within the soilmatrix. A critical measurement in this regard is precise determinationof the graphite content at all points in the injected lens, whichlargely dictates the electrical continuity of the lens. Graphite contentcan be measured in a number of ways because of its diverse properties.Graphite is the hexagonally crystallized allotrope of carbon formed fromthe metamorphism of carbonaceous material in sedimentary rocks. It hasperfect cleavage in one direction, and thus exists as thin, elongatedflakes which are flexible and prone to further foliation and breakage.Organic carbon and iron oxide are common impurities. Graphite is a goodconductor of heat and electricity, is almost chemically inert, and isextremely refractory.

DESCRIPTION OF PREFERRED EMBODIMENTS

There follows a description of various preferred embodiments of thepresent invention. These working examples are intended to beillustrative only, and are not intended to in any way limit the scope ofthe present invention which is herein claimed.

EXAMPLE 1

Model for Predicting Pressure and Velocity Distributions

A study was undertaken to investigate selected physical propertiesinvolved in utilizing pneumatic fracturing together with pneumaticinjection of dry media to carry out in situ vitrification (ISV). Modelanalyses were performed in parallel with bench scale experiments.Predictions relating to pressure and velocity distributions were madeusing an equation which took into account gas compressibility effects,and assumed that conditions were isothermal. For laminar flow theexponent in the equation relating to the nature of the flow was 3, thusestablishing a cubic relationship between flow and aperture. By solvingthe equation for P₂, it was possible to calculate the pressuredistribution in the formation at selected radii. The pressure at theinjection point, P₁, was estimated to be 40 psi based on a study offracture maintenance pressure. The fracture aperture was assumed to be0.4 in. (1 cm) and the injection flow rate was assumed to be 3,000 cfm.The pressure drop along the fracture was calculated to be minimal owingto the relatively large aperture. This model does not, however, takeinto account formation leakoff.

The second part of the model estimated the velocity distribution in thediscrete fracture. A finite difference approach was used, taking intoaccount air leakoff into the formation. Prediction of air velocity wascritical to the integrated ISV system, since velocity would determinethe maximum radius of fracture penetration, as well as the distancewhich the graphite/glass frit dry media could be transported through thesoil formation. The physical model used for velocity distributionassumed leakoff of the injected air into the formation across the upperand lower boundaries of the fracture according to the pneumatic gradientthrough the adjacent porous medium. The leakoff was calculated insuccessive annular rings centered on the injection point. Thus, flowcorrespondingly declined with increasing radius. The model was solvedusing a range of assumed values for aperture (b), pneumatic conductivity(K_(p)), and pneumatic gradient (i_(p)). Typical calculated results areset out in the table of values below.

                  TABLE 1    ______________________________________    K.sub.p *             i.sub.p **     b      max radial    (m/s)    (unitless)     (m)    distance (m)    ______________________________________    0.0007    4500/1500     0.05   0    0.0007   1500/500       0.05   0    0.00007  2250/750       0.025  1.1    0.000007 1500/500       0.05   5.3    0.000007  4500/1500     0.05   2.9    ______________________________________     *The hydraulic conductivity of a particular soil formation of interest wa     reported to range from 0.001 to 0.1 m/s. Converting to pneumatic     conductivity, and extending the lower boundary of K.sub.p one order of     magnitude to account for caking effects, a range of 0.000007 to 0.0007 m/     was obtained and used for the analysis.     **The pneumatic gradient for leakoff was estimated at a depth of 5 m. Due     to the absence of an atmospheric boundary, the downward gradient was     assumed to be one third of the upward gradient. Key: upward     gradient/downward gradient i.sub.p was taken as the average of the     gradients.

It was found that flow dissipated quickly, although an effective radiusup to a few meters was attainable. The analysis also predicted minimalpenetration for the combination of high formation permeability andgradient. However, this model did not take into account the results thatcould be obtained using the high velocity planar nozzle of the presentinvention.

Model for Predicting Transport of Injected Media in Discrete Fractures

The potential for vertical and/or horizontal segregation andstratification of the graphite/glass frit particles during the dry mediainjection was investigated. The mechanics of particle transport in anopen pneumatic fracture were determined to be similar to those ofsediment transport in river beds. The threshold for grain movement was afunction of fluid viscosity and particle characteristics, e.g., shape,size, sorting of grains, and density. The method used to model thetransport of graphite/glass frit in the discrete fracture was theShields diagram method, one of the most widely used mathematicalrelationships for determining the critical suspension velocity, which isthe minimum velocity at which the particle remains in suspension, andcan be used for particle transport in air as well as in water. Thisrelationship plots dimensionless shear stress τ* against grain Reynoldsnumber R_(eg), which is also a dimensionless quantity. The dimensionlessshear stress increases with increasing bed shear stress and velocitydecreases with increasing density and size of particles according to thefollowing equation: ##EQU4## where Υ_(s) =specific gravity of theparticles

Υ_(f) =specific gravity of the fluid

d=particle diameter

τ₀ =boundary shear stress

Friction velocity in the grain Reynolds number is a measure of theturbulent eddying, and is therefore an indication of turbulence at thegrain-fluid boundary. An increase in grain Reynolds number means eitheran increase in friction velocity and turbulence, an increase in graindiameter or a decrease in kinematic viscosity. The points above thecurve indicate the condition under which the particles are in motion andcapable of being transported, while the points below are stationary. Thecritical suspension velocity for graphite and glass frit deposition fromthe air stream using the Shields diagram method were estimated to rangefrom 0.37 m/s-0.38 m/s and 0.35 m/s-0.39 m/s, respectively. Thecalculated values were considered estimates only, since it was necessaryto extrapolate the data beyond the published extrapolation line. Thesimilarity of critical suspension velocities between both particle typessuggested that there was little potential for segregation.

EXAMPLE 2

Integration of Pneumatic Fracturing and In Situ Vitrification

This demonstration of the use of pneumatic fracturing and pneumaticinjection of dry media comprising graphite particles and glass frit inorder to carry out in situ vitrification was carried out at a formationin the Northwestern United States, referred to hereafter as the "NW"site, which is a glaciofluvial deposit consisting of coarse-grainedsoils, which is notably different from the fine-grained formations withlow permeability that were the subject of other studies. Bench scaleresults established that the soils of this formation could bepneumatically intruded and that an electrically conductive starter pathcould be established. A simplified mathematical model was developed andused to predict the effective radius at the field scale. The mostsignificant formation parameters which were found to affect the processwere permeability, natural moisture content, and density. Theseexperimental parameters exhibited both independent and interactiveeffects on the process effectiveness.

A pilot feasibility test was performed at the NW site with promisingresults. A starter path was created at a depth of 14 feet at twosettings. Following insertion of the starter path, resistancemeasurements were made across the electrodes which showed that asuitable electrically conductive plane had been established. The resultsof these electrical measurements showed that the injected media reducedformation resistance from a natural level of 100,000-500,000 ohms downto less than 100 ohms. The resistance level established by the injectionwas considered low enough to support a melt, so the first test settingwas powered up. After attaining a power level of 20 kW, the test wasterminated due to increasing melt resistance. Subsequent excavation ofthese electrodes show that although a melt had begun around each of theelectrodes, it had not coalesced into a continuous vitrified mass. Thefailure of this first attempt was attributed to insufficient power aswell as the marginal interface between the conductive lens and theelectrode.

A second vitrification attempt was made at the second test setting,which followed an exploratory excavation to delineate the extent of theconductive lens and to improve its interface with the electrodes. Thebasic setup for this test setting is schematically represented in FIG.20. During this second attempt, a melt was sustained for a 9 hourduration with power levels ranging up to 300 kW. Subsequent excavationshowed that the vitrified soil mass weighed 2 tons and was composed ofhigh-quality glass. This was believed to have been the first in situmelt ever initiated below the ground surface. The power requirements forthis subsurface melt were 30% less than that typically observed forsurface initiated melts, i.e., 0.71 kW/kg vs. 1.0 kW/kg. This findingindicates that subsurface initiation will probably have significant costadvantages over surface initiation, since power represents a substantialpercentage of the cost of the basic in situ vitrification technology,and that these cost savings will more than offset the added cost ofsubsurface injection of dry media to establish the starter path.

What is claimed is:
 1. A method for pneumatically injectingsubstantially dry media into a soil formation, comprising:a)pneumatically fracturing said soil formation, comprising:i) inserting atubular probe partially into the soil formation such that at least oneorifice of a nozzle fluidly connected with said tubular probe ispositioned at a predetermined height; and ii) supplying a pressurizedgas on a continuous basis into said tubular probe such that theresulting pressurized gas stream travels through said at least oneorifice into said soil to produce a fracture network in said soilformation; b) preserving said fracture network in a dilated state orotherwise thereafter utilizing said fracture network, by maintainingcontinuous injection of said gas; c) introducing substantially dry mediainto said gas stream, optionally from a pressurized supply of said drymedia, while maintaining the gas to media ratio in the range of fromabout 100 to 1 to about 10,000 to 1 on a volume to volume basis, inorder to assure adequate dispersion and distribution of the dry mediathrough the soil formation in predetermined patterns; d) continuinginjection of said dry media into said fracture network until the desiredamount and predetermined distribution pattern for said dry media havebeen achieved; and e) as desired or necessary, repeating steps a)through d) on a sequential basis in order to treat additional portionsof said soil formation.
 2. A method according to claim 1 wherein saidpressurized gas is compressed air; wherein there is additionally presenta nozzle fluidly connected with said tubular probe, said nozzle being ahigh velocity substantially planar nozzle whose injection aperture is asubstantially 360° opening of a predetermined height, and whose internaljunction with said tubular probe comprises a forcing cone having auniform parabolic or functionally similar slope to provide maximumacceleration to said gas steam and its entrained dry media; and whereinsaid dry media comprises one or more members selected from the groupconsisting of silica, including sand and glass frit; carbon, includinggraphite and powdered charcoal; powdered metals including copper,nickel, tin, zinc, iron, magnesium, aluminum, phosphorus, chromium,cadmium, palladium, platinum, or alloys and salts thereof; particles andbeads of synthetic resin, including polymers, copolymers and terpolymersof polyacrylates including those prepared from acrylic and methacrylicacid; polyolefins including those made from ethylene, propylene, andbutylene; polyvinyl chloride; polystyrenes; polyesters; polyimides;polyurethanes; polyamides; and polycarbonates; and mixtures of any ofthese; organic compounds capable of remediating a soil formationcontaminated with non-naturally occurring compositions, comprisingchlorinated organic compounds, including hydrocarbons, by oxidizing,reducing, or neutralizing said non-naturally occurring compositions,including dechlorinating chlorinated hydrocarbons, by reacting with saidnon-naturally occurring compositions to produce non-contaminatingreaction products, and by catalyzing the chemical transformation of saidnon-naturally occurring compositions into non-contaminating products,including catalysis by enzymatic action; and compositions which promotethe growth and activity of microorganisms in said soil formation.
 3. Amethod according to claim 2 wherein said compositions which promote thegrowth and activity of microorganisms comprise one or more membersselected from the group consisting of direct acting or time releasenutrient pellets, buffers, oxygen sources and inocula in granular form.4. A method for reducing or eliminating non-naturally occurring,subsurface, liquid contaminants from one or more soil formations,comprising:a) pneumatically fracturing said soil formation(s),comprising:i) inserting a tubular probe partially into said soilformation such that a nozzle fluidly connected with said tubular probeis positioned at a predetermined height, wherein said nozzle is a highvelocity substantially planar nozzle whose injection aperture is asubstantially 360° opening of a predetermined height, and whose internaljunction with said tubular probe comprises a forcing cone having auniform parabolic or functionally similar slope to provide maximumacceleration to said gas steam and dry media to be entrained therein;and ii) supplying a pressurized gas on a continuous basis into saidtubular probe such that the resulting pressurized gas stream travelsthrough said aperture of said nozzle into said soil to produce afracture network in said soil formation(s); b) preserving said fracturenetwork in a dilated state or otherwise thereafter utilizing saidfracture network, by maintaining continuous injection of said gas; c)introducing substantially dry media into said gas stream from anoptionally pressurized supply of said dry media, while maintaining thegas to media ratio in the range of from about 100 to 1 to about 10,000to 1 on a volume to volume basis, in order to assure adequate dispersionand distribution of the dry media through the soil formation inpredetermined patterns; d) continuing injection of said dry media untilsuitable amounts and predetermined distribution pattern for said drymedia have been achieved; e) as desired or necessary, repeating steps a)through d) on a sequential basis in order to treat additional portionsof said soil formation(s); and f) where said contaminants are beingreduced or eliminated, maintaining a low volume flow of said pressurizedgas throughout said fracture network and adjacent portions of said soilformation(s), optionally with the assistance of means for exertingreduced pressure thereon, for a time sufficient to oxidize, reduce,neutralize, transform by reaction or catalysis or otherwise degradeand/or remove said contaminants from said soil formation(s); or g) wheresaid contaminants are being isolated, using in situ vitrification as themeans for producing such isolation, comprising:i) using as said drymedia one or more compositions which when dispersed and distributed insaid soil formation in suitable amounts and predetermined patternscreate conductive resistance starter paths; and ii) applying electricalcurrent to the conductive resistance starter paths using at least twoelectrodes suitably placed in said soil formation, in an amount and fora time sufficient to produce electrical resistance heating of said soilformation in a melt zone between said electrodes to a temperature abovea melting point of all or a portion of said soil formation sufficient toproduce a solid, vitrified, isolating mass.
 5. A method according toclaim 4 wherein the pressurized gas is compressed air; wherein thereduced pressure exerted on said fracture network and adjacent portionsof said soil formation(s) is created by one or more extraction wellshaving vacuum pumps attached thereto; and wherein one or more vent wellsare created to supply additional amounts of air to said soilformation(s).
 6. A method according to claim 4 wherein said nozzle isdisposed substantially perpendicular to said tubular probe.
 7. A methodaccording to claim 4 wherein said soil is a non-cohesive soil comprisinggranular sands and gravels which do not exhibit brittle behavior andfail to form a fracture network; and wherein said high velocity nozzle,instead of being at a 90° angle to said vertical tubular probe, saidnozzle directs said pressurized gas stream into said surrounding soilformation at an angle calculated to be in approximately the same planeas the plane of said soil formation, comprising the angle between theplane of said nozzle through its aperture and the axis of said tubularprobe.
 8. A method according to claim 4 wherein said method is carriedout by establishing an in situ bioremediation cell in said one or moresoil formations in order to degrade said contaminants; wherein there isemployed as the dry media, nutrient material which will enhance thegrowth and activity of microorganisms present in said contaminated soilformation, which are capable of degrading or reducing said contaminantsand thereby eliminating them.
 9. A method according to claim 8 whereinsaid nutrient materials comprise inocula, agents to generate the desiredpH, buffers to maintain said pH, and nutritive substances; and whereinsaid gas which is injected continuously is oxygen-containing.
 10. Amethod according to claim 9 wherein said nutritive substance has afragile time release coating.
 11. A method according to claim 4 whereinsaid method for reducing or eliminating non-naturally occurring,subsurface, liquid contaminants from one or more soil formations iscarried out by introducing into said one or more soil formationschemical agents which reduce, oxidize, cleave, decompose, chelate orcomplex, or otherwise enter into chemical reactions with saidcontaminants whereby the qualities which make them undesirable arepermanently altered.
 12. A method according to claim 1 for isolatingnon-naturally occurring, subsurface, liquid contaminant zones within oneor more soil formations by creating vitrified underground structureswhich produce such isolation, comprising:a) using as said dry media,graphite or graphite mixed with glass frit, whereby there is createdconductive starter paths at a desired depth, and in a desired locationin said soil formation; b) applying electrical current to saidconductive starter paths by the use of electrodes in a known manner; andwherein the gas stream used in the initial pneumatic fracturing and incontinuous flow during dry media introduction, is not oxygen containing.13. A method according to claim 4 wherein said one or more soilformations do not exhibit self-propping behavior and comprise softer,sensitive clays; and wherein there is used as said dry media a granularpropping agent.
 14. A method according to claim 13 wherein said granularpropping agent is sand; and wherein said method creates and maintains acontinuous plane of fluid flow channels which establish connectivity inthe soil formation and thereby accelerate contaminant treatment byconventional techniques.
 15. A method for reducing, eliminating, orisolating non-naturally occurring, subsurface, liquid contaminants fromone or more soil formations, comprising:a) pneumatically fracturing saidsoil formation(s), comprising:i) inserting a tubular probe partiallyinto said soil formation such that a nozzle fluidly connected with saidtubular probe is positioned at a predetermined height, wherein saidnozzle is a high velocity directional nozzle capable of delivering thepressurized gas to all or any significant circular section or arc of thesurrounding soil formation, from about 15° to substantially 360°, thesection being either defined and fixed, or else being determinable andselectable by operation of said nozzle, including a substantially planarnozzle whose injection aperture is a 360° opening of a predeterminedheight, and wherein the internal junction of the nozzle means with thetubular probe comprises a forcing cone having a uniform parabolic orfunctionally similar slope to provide maximum acceleration to the gasstream and dry media entrained therein immediately before entering thesoil formation; and wherein said substantially planar nozzle whoseinjection aperture is said 360° opening of a predetermined height,directs said pressurized gas stream out through its aperture and intosaid surrounding soil formation at an angle calculated to be inapproximately the same plane as the plane of said soil formationsubstratum, said angle being the angle between the plane of said nozzlethrough its aperture and a plane perpendicular to the axis of saidtubular probe; and ii) supplying a pressurized gas on a continuous basisinto said tubular probe such that the resulting pressurized gas streamtravels through said aperture of said nozzle into said soil to produce afracture network in said soil formation(s); b) preserving said fracturenetwork in a dilated state by maintaining continuous injection of saidgas; c) introducing substantially dry media into said gas stream,optionally from a pressurized supply of said dry media, whilemaintaining the gas to media ratio in the range of from about 100 to 1to about 10,000 to 1 on a volume to volume basis in order to assure thecontinued dilation of said fracture network during injection of said drymedia; d) continuing injection of said dry media until said fracturenetwork is filled with said dry media to the extent desired; and e) asdesired or necessary repeating steps a) through d) on a sequential basisin order to treat additional portions of said soil formation(s); and f)where said contaminants are being reduced or eliminated, maintaining alow volume flow of said pressurized gas throughout said fracture networkand adjacent portions of said soil formation(s), optionally with theassistance of means for exerting reduced pressure thereon, for a timesufficient to oxidize, reduce, neutralize, transform by reaction orcatalysis or otherwise degrade and/or remove said contaminants from saidsoil formation(s); or g) where said contaminants are being isolated,using in situ vitrification as the means for producing such isolation,comprising:i) using as said dry media one or more compositions whichwhen dispersed and distributed in said soil formation in suitableamounts and predetermined patterns create conductive resistance starterpaths; and ii) applying electrical current to the conductive resistancestarter paths using at least two electrodes suitably placed in said soilformation, in an amount and for a time sufficient to produce electricalresistance heating of said soil formation in a melt zone between saidelectrodes to a temperature above a melting point of all or a portion ofsaid soil formation sufficient to produce a solid, vitrified, isolatingmass.